WORKS   OF  G.   C.   WHIPPLE 

PUBLISHED   BY 

JOHN    WILEY   &    SONS. 


The  Microscopy  of  Drinking-water. 

Second  edition,  revised.  8vo,  xii+338  pages, 
figures  in  the:  text  and  19  full-page  half-tones. 
Cloth,  $3.50. 

The  Value  of  Pure  Water. 

Large  i2mo,  viii+  84  pages.     Cloth,  $1.00, 

Typhoid  Fever  — Its  Causation,  Transmission  and 
Prevention. 

Introduction  by  WILLIAM  T.  SEDGWICK,  Ph.D. 
Large  12010,  xxxvi  +  407  pages,  50  figures.  Cloth, 
$3.00  net. 


THE 

MICROSCOPY 

OF 

DRINKING-WATER. 


BY 

GEORGE    CHANDLER    WHIPPED, 

Professor  of  Sanitary  Engineering,  Harvard  University. 


SECOND   EDITION,   REVISED. 
SECOND    THOUSAND. 


A  >'    :i'V*v%:  h 


NEW    YORK: 

JOHN    WILEY    &    SONS. 

LONDON:    CHAPMAN   &   HALL,   LIMITED. 

1911 


Copyright,  1899,  1905, 

BY 
GEORGE  CHANDLER  WHIPPL 


SfOLOfir  LIEMARY 


THE  SCIENTIFIC  PRF3S 

MMCRT    DRUMMOND   AND   COMPANT 

BROOKLVN,    N.  V. 


DEDICATED    TO    MY    FATHER, 

•Josepb  Ik.  Mbipple, 


891712 


PREFACE. 


THIS  book  has  a  twofold  purpose.  It  is  intended 
primarily  to  serve  as  a  guide  to  the  water-analyst  and  the 
water-works  engineer,  describing  the  methods  of  micro- 
scopical examination,  assisting  in  the  identification  of  the 
common  microscopic  organisms  found  in  drinking-water  and 
interpreting  the  results  in  the  light  of  environmental  studies. 
Its  second  purpose  is  to  stimulate  a  greater  interest  in  the 
study  of  microscopic  aquatic  life  and  general  limnology  from 
the  practical  and  economic  standpoint. 

The  work  is  elementary  in  character.  Principles  are 
stated  and  briefly  illustrated,  but  no  attempt  is  made  to 
present  even  a  summary  of  the  great  mass  of  data  that  has 
accumulated  upon  the  subject  during  the  last  decade.  The 
illustrations  have  been  drawn  largely  from  biological  researches 
made  at  the  laboratory  of  the  Boston  Water  Works  and  from 
the  reports  of  the  Massachusetts  State  Board  of  Health.  In 
considering  them  one  should  remember  that  the  environ- 
mental conditions  of  the  Massachusetts  water-supplies  are  not 
universal,  and  that  every  water-supply  must  be  studied  from 
the  standpoint  of  its  own  surroundings.  So  far  as  the  micro- 
scopic organisms  are  concerned,  however,  the  troubles  that 


vi  PREFA  CE. 

they  have  caused  in  Massachusetts  may  be  considered  as 
typical  of  those  experienced  elsewhere. 

The  descriptions  of  the  organisms  in  Part  II  are  necessarily 
brief  and  limited  in  number.  The  organisms  chosen  for 
description  are  those  that  are  most  common  in  the  water- 
supplies  of  New  England,  and  those  that  best  illustrate  the 
most  important  groups  of  microscopic  animals  and  plants. 
In  many  cases  whole  families  and  even  orders  have  been 
omitted,  and  some  readers  will  doubtless  look  in  vain  for 
organisms  that  to  them  seem  important.  The  omissions  have 
been  made  advisedly  and  with  the  purpose  of  bringing  the 
field  of  microscopic  aquatic  life  within  the  scope  of  a  practical 
and  elementary  survey.  For  the  same  reason  the  descriptions 
stop  at  the  genus  and  no  attempt  has  been  made  to  describe 
species  and  varieties.  Notwithstanding  this  it  is  believed 
that  the  illustrations  and  descriptions  are  complete  enough  to 
enable  the  general  reader  to  obtain  a  true  conception  of  the 
nature  of  the  microscopic  life  in  drinking-water  and  to  appre- 
ciate its  practical  importance.  To  the  student  they  must 
serve  as  a  skeleton  outline  upon  which  to  base  more  detailed 
study. 

The  illustrations,  for  the  greater  part,  have  been  drawn 
from  living  specimens  or  from  photo-micrographs  of  living 
specimens,  but  some  of  them  have  been  reproduced  from 
published  works  of  standard  authority.  Among  these  may 
be  mentioned:  Pelletan  and  Wolle  on  the  Diatomaceae; 
Woll£,  Rabenhorst,  and  Cooke  on  the  Chlorophyceae  and 
Cyanophyceae ;  Zopf  on  the  Fungi;  Leidy,  Biitschli,  and 
Kent  on  the  Protozoa;  Hudson  and  Goss  on  the  Rotifera; 
Baird  and  Herrick  on  the  Crustacea;  Lankester  on  the  Bryo- 
zoa;  Potts  on  the  Spongidae;  and  Griffith  and  Henry  on 
miscellaneous  organisms. 


PREFACE.  vil 

This  book  has  been  prepared  during  the  leisure  moments 
of  a  busy  year.  Its  completion  has  been  made  possible  by 
the  kind  assistance  of  my  present  and  former  associates  in 
the  laboratories  of  the  Boston  and  Brooklyn  water-supply 
departments  and  of  other  esteemed  friends,  to  all  of  whom  I 
tender  my  sincere  thanks.  I  desire  also  to  acknowledge  the 
valuable  assistance  of  my  wife,  Mary  R.  Whipple,  in  revising 
the  manuscript  and  correcting  the  proof.  To  many  others  I 
am  indebted  indirectly,  and  among  them  I  cannot  refrain  from 
mentioning  the  names  of  Prof.  Wm.  T.  Sedgwick  of  the 
Massachusetts  Institute  of  Technology;  Mr.  Geo.  W.  Rafter, 
C.E.,  of  Rochester,  N.  Y. ;  and  Mr.  Desmond  FitzGerald, 
C.E.,  formerly  Superintendent  of  the  Boston  Water  Works 
and  now  Engineer  of  the  Sudbury  Department  of  the  Metro- 
politan Water  Works.  To  Prof.  Sedgwick  and  Mr.  Rafter 
water-analysts  are  indebted  for  the  most  satisfactory  practical 
method  of  microscopical  examination  of  drinking-water  yet 
devised,  and  Mr.  FitzGerald  will  be  remembered  not  only  as 
an  eminent  engineer  but  as  the  founder  and  patron  of  the 
first  municipal  laboratory  for  biological  water-analysis  in  this 
country. 

GEORGE  CHANDLER  WHIPPLE. 

NEW  YORK,  January,  1899. 


PREFACE  TO  THE  SECOND  EDITION. 


THE  author  has  been  much  gratified  to  note  the  influence 
which  the  first  edition  of  the  " Microscopy  of  Drinking-water" 
has  had  in  stimulating  the  study  of  the  microscopic  organisms 
from  practical  standpoints.  The  methods  of  examination  there 
set  forth  appear  to  have  stood  the  test  of  experience.  They  have 
recently  received  the  official  endorsement  of  the  Committee  on 
Standard  Methods  of  Water  Analysis  of  the  Laboratory  Section 
of  the  American  Public  Health  Association.  Results  obtained 
by  them  have  proved  of  great  value  in  problems  concerning  the 
quality  of  water  supplies,  and  in  many  instances  they  have  been 
presented  as  testimony  in  court  cases.  No  change  of  methods 
is  here  suggested. 

Since  the  publication  of  the  first  edition  new  applications 
of  the  methods  of  microscopical  examination  have  been  made. 
Processes  for  treating  water  supplies  deleteriously  affected  with 
microscopic  organisms  have  been  studied  with  considerable  care. 
Perhaps  the  most  important  of  these  has  been  the  use  of  copper 
sulphate  as  an  algicide.  Recent  developments  have  brought  to 
light  but  few  new  organisms  worth  mentioning  by  reason  of 
their  harmful  effects  on  water  supplies,  but  many  new  instances 
of  objectionable  growths  of  the  common  organisms  have  been 
placed  on  record,  and  the  importance  of  the  subject  is  now  appre- 
ciated as  never  before. 

In  this  second  edition  Part  I  has  been  revised  and  somewhat 
extended,  but  Part  II  remains  practically  unchanged. 

G.  C.  W. 


CONTENTS. 


PART    I. 

CHAPTER    I. 

HISTORICAL. 

PAGB 

Early  Investigators  in  Europe  and  the  United  States. — Cloth  Method. — 
Kean's  Sand  Method. — SedgWick's  Improvements. — Sedgwick-Rafter 
Method. — Recent  Improvements. — Plankton  Studies  in  Europe  and 
America i 

CHAPTER  II. 

THE  OBJECT  OF  THE  MICROSCOPICAL  EXAMINATION. 

Sanitary  Analyses. — Interpretation  of  Analyses. — Use  of  Microscopical 
Examination  in  Indicating  Sewage  Contamination — in  Explaining 
the  Chemical  Analyses — in  Explaining  the  Turbidity  and  Odor  of 
Waters — in  Showing  the  Source  of  Certain  Waters — in  Studying  the 
Food  of  Fishes 8 

CHAPTER  III. 

METHODS  OF  MICROSCOPICAL  EXAMINATION. 

Sedgwick-Rafter  Method.— The  Filter.— Concentration.— The  Cell.— 
The  Microscope. — Enumeration. — Sources  of  Error. — Precision  of  the 
Method. — Results  of  Examination. — The  Standard  Unit. — Records. — 
The  Plankton  Net  Method.— The  Plankton  Pump.— The  Planktonokrit . .  15 

CHAPTER  IV. 

MICROSCOPIC  ORGANISMS  IN  WATER  FROM  DIFFERENT  SOURCES. 

Rain-water. — Ground -water. — River-\vater. — Canals. — Raphidomonas  in  the 

Lynn  Water.— Pond -water.— Filtered  Water 41 

ix 


X  CONTENTS. 

CHAPTER  V. 

LIMNOLOGY. 

PAGB 

Physical  Properties  of  Water. — Compressibility. — Density. — Mobility. — 
Thermal  Stratification. — Diathermancy. — Temperature  of  Lakes. — 
Methods  of  Observation. — Thermophone. — Seasonal  Variation  of  Tem- 
perature.— Periods  of  Circulation. — Periods  of  Stagnation. — Thermo- 
cline. — Classification  of  Lakes  according  to  Temperature. — Transmis- 
sion of  Light  by  Water. — Color  of  Water. — Method  of  Determination. — 
Seasonal  Change  of  Color. — Bleaching  of  Color  by  Sunlight. — Turbidity 
of  Water. — Methods  of  Determination. — Transparency  of  Water. — 
Absorption  of  Light  by  Water 51 

CHAPTER  VI. 

GEOGRAPHICAL  DISTRIBUTION  OF  MICROSCOPIC  ORGANISMS. 

Common  Organisms  Classified  according  to  the  Frequency  of  Their  Occur- 
rence.— Statistics  of  Their  Occurrence  in  Massachusetts  Surface-water 
Supplies. — Relation  of  Each  Class  of  Organisms  to  the  Sanitary  Chemical 
Analyses. — Effect  of  Oxygen  and  Carbonic  Acid 81 

CHAPTER  VII. 

SEASONAL  DISTRIBUTION  OF   MICROSCOPIC  ORGANISMS. 

Seasonal  Succession  of  Organisms. — Spring  and  Autumnal  Growths  of 
Diatoms. — Explanation  of  this  Seasonal  Distribution. — Effect  of  Tem- 
perature.— Effect  of  Light. — Heliotropism. — Food-material. — Stagna- 
tion.— Seasonal  Distribution  of  Chlorophyceae,  Cyanophyceae,  Schizo- 
phycese,  Fungi,  Protozoa,  Rotifera,  Crustacea 98- 

CHAPTER  VIII. 

HORIZONTAL  AND  VERTICAL  DISTRIBUTION  OF  MICROSCOPIC 
ORGANISMS. 

Littoral  Organisms. — Limnetic  Organisms. — Effect  of  Winds  and  Currents 
on  Horizontal  Distribution. — Conditions  Affecting  Vertical  Distribution. 
— Growth  above  the  Thermocline. — Effect  of  the  Specific  Gravity  of 
Organisms. — Peculiar  Vertical  Distribution  of  Mallomonas. — Protozoa. 
— Statistics  of  Vertical  Distribution 1091 

CHAPTER  IX. 

ODORS  IN  WATER-SUPPLIES. 

The  Senses  of  Taste  and  Odor. — Odors  Caused  by  Organic  Matter. — Odors 
of  Decomposition. — Odors  Caused  by  Living  Organisms. — Character  of 
Odoriferous  Substances. — Intensity  of  Odors. — Characteristic  Odors  of 
Different  Organisms. — Extent  to  which  Water-supplies  are  Afflicted  with 
Odors. — Cucumber  Odor  Not  Caused  by  Fresh-water  Sponge.— Cucum- 
ber Odor  in  Boston  Water n 


CONTENTS.  XI 

CHAPTER  X. 

STORAGE  OF  SURFACE-WATER. 

PAGB 

Clean  Watersheds. — Effect  of  Swamps. — Anabaena  in  Cedar  Swamp. — 
Drainage  of  Swamps. — Self-draining  Watersheds. — Self-draining  Reser- 
voirs.— Stagnation  of  Water  in  Deep  Reservoirs. — Lake  Cochituate. — 
Removal  of  Organic  Matter  from  the  Sides  and  Bottom  of  Reservoirs. — 
Blow-off  at  the  Bottom  of  Deep  Reservoirs. — Effect  of  Algae  and  Pro- 
tozoa on  Bacteria 134 

i 
CHAPTER  XI. 

STORAGE  OF  GROUND-WATER. 

Ground-water  to  be  Stored  in  the  Dark. — Growth  of  Organisms  in  Open 
Reservoirs. — Storage  of  Surface-water  and  Ground-water  Together. — 
Asterionella  in  Brooklyn  Water-supply. — Storage  of  Impure  Ground- 
Water. — Crenothrix. — Storage  of  Filtered  Water 148 

CHAPTER  XII. 
METHODS  OF  TREATMENT. 

Aeration.  — Decarbonation , — By-passes. — House  Filters. — Slow  Sand  Filtra- 
tion.— Mechanical  Filtration. — Springfield  Experiments. — Use  of  Copper 
Sulphate 153 

CHAPTER  XIII. 

GROWTH  OF  ORGANISMS  IN  WATER-PIPES. 

Effect  of  Pipes  upon  the  Biology  of  Water. — Temperature. — Microscopic 
Organisms. — Amorphous  Matter. — Bacteria. — Effect  of  Water  upon  the 
Biology  of  Water-pipes. — Hamburg. — Rotterdam. — Boston. — Food  of 
Organisms  Dwelling  in  Pipes. — Polyzoa. — Fresh-water  Sponge. — Effect 
of  Pipe-moss. — Friction. — Odor  of  Water. — Paludicella  in  Brooklyn. . . .  160 


PART   II. 

CHAPTER  XIV. 

CLASSIFICATION  OF  MICROSCOPIC  ORGANISMS. 
Table  of  Classification 


CHAPTER  XV. 

DIATOMACE&. 

Diatom  Cells.  —  Shape  and  Size.  —  Markings.  —  Cell-contents.  —  External 
Secretions.  —  Movement.  —  Multiplication.  —  Reproduction.  —  Classifica- 
tion. —  Description  of  Genera  .............................  .......  173 


xii  CONTENTS. 

CHAPTER  XVI. 
SCHIZOMYCETES. 

PAGB 

Schizophyceas. — Schizomycetes. — Characteristics. — Description   of    Genera..   192 

CHAPTER  XVII. 

CYANOPHYCE&. 

Characteristics. — Description  of  Genera 195 

CHAPTER  XVIII. 

CHLOROPHYCE&. 
Algae. — Chlorophyceae. — Characteristics. — Description  of  Genera 204 

CHAPTER  XIX. 

FUNGI. 
Characteristics. — Description  of  Genera 221 

CHAPTER  XX. 

PROTOZOA. 

General     Characteristics.  —  The     Protozoan     Cell.  —  Rhizopoda. — Mastigo- 

phora. — Infusoria. — Description  of  Genera 225 

CHAPTER  XXI. 

ROT  IF  ERA. 
Characteristics. — Description  of  Genera 248 

CHAPTER  XXII. 

CRUSTACEA. 
Characteristics. — Description  of  Genera „ 256 

CHAPTER  XXIII. 

BRYOZOA  (POLYZOA). 

Characteristics. — Description  of  Genera.  .  .  . 261 

CHAPTER  XXIV. 

SPONGID&. 
Characteristics. — Description  of  Genera. 264. 


CONTENTS.  Xlii 

CHAPTER  XXV. 

MISCELLANEOUS  ORGANISMS. 

PAGE 

Aquatic  Plants. — Aquatic  Animals 267 


APPENDIX  A.  COLLECTION  OF  SAMPLES 269 

"  B.  TABLES  AND  FORMULAE ." 272 

"  C.  BIBLIOGRAPHY 276 

"  D.  GLOSSARY  TO  PART  II 311 

INDEX 315 


THE 
MICROSCOPY    OF    DRINKING-WATER. 


PART  I. 

CHAPTER    I.. 
HISTORICAL/ 


THE  study  of  the  microscopic  organisms  in  water  dates 
back  to  the  seventeenth  century.  With  the  invention  of  the 
compound  microscope  enthusiastic  observers  began  to  search 
ponds  and  streams  and  ditches  for  new  and  varied  kinds  of 
microscopic  life.  Among  the  pioneers  in  this  field  of  Natural 
History  were  Hooke(i665),  Leeuwenhoek  (1675),  Ray  (1724), 
Hudson  (1762),  Miiller  (1773),  Dillwyn  (1809),  Kutzing 
(1834),  Ehrenberg  (1836),  Dujardin  (1841),  and  Stein  (1849). 

It  was  not  until  1850  that  the  study  of  the  organisms  in 
drinking-water  was  recognized  as  having  a  practical  sanitary 
value.  Dr.  Hassall  of  London  was  the  first  to  call  attention 
to  it.  His  method  of  procedure  is  unknown,  but  in  all  proba- 
bility it  consisted  of  the  examination  of  a  few  drops  of  the 
sediment  collected  in  a  deep  vessel  after  allowing  the  water 
to  stand  for  a  longer  or  shorter  interval.  Radlkofer  (1865) 
of  Munich,  and  Cohn  (1870),  Hirt  (1879)  an<^  Hulwa  of  Bres- 
lau,  pursued  the  study  and  emphasized  its  importance,  but 
they  made  no  radical  improvement  in  the  method. 

In   1875   Dr.  J.  D.  Macdonald  of  London  suggested  im- 


2  THE    MICROSCOPY   OF  DRINKING-WATER. 

provements  in  the  sedimentation  method,  and  made  a  rude 
attempt  to  obtain  quantitative  results  by  allowing  the  water 
to  settle  for  a  definite  length  of  time,  collecting  the  sediment 
on  a  removable  glass  disk  or  watch-glass  at  the  bottom  of  a 
tall  jar,  and  afterwards  transferring  this  glass  disk  with  its 
accumulated  sediment  to  the  stage  of  the  microscope  for 
direct  examination.  » 

In  1884  Dr.  H.  C.  Sorby  of  England  attempted  to 
obtain  a  more  exact  enumeration  by  passing  a  gallon  of  the 
sample  through  a  fine  sieve  (200  meshes  to  an  inch)  and  then 
washing,  the  collected  organisms  into  a  dish  and  in  some  way 
counting  then. 

In  America,  ?m  pott  ant  researches  were  made  by  Torrey, 
Vorce,  Mills,  Leeds,  Potts,  Nichols,  Farlow,  and  others,  but 
previous  to  1888  the  work  was  chiefly  of  a  qualitative 
character. 

In  1887  the  Massachusetts  State  Board  of  Health  began  a 
systematic  examination  of  all  the  water-supplies  of  the  State, 
and  two  years  later  the  State  Board  of  Health  of  Connecticut 
began  a  similar  but  less  extensive  series  of  examinations.  In 
1889  the  Water  Board  of  the  City  of  Boston  established  a 
biological  laboratory*  at  the  Chestnut  Hill  Reservoir  for  the 
purpose  of  studying  systematically  the  biological  character  of 
the  various  sources  of  supply.  In  1893  a  small  laboratory 
was  established  by  the  Public  Water  Board  of  the  City  of 
Lynn,  Mass.  In  1897  Mt.  Prospect  Laboratory,  connected 
with  the  Department  of  Water  Supply  of  Brooklyn,  N.  Y., 
was  equipped  and  put  in  operation.  It  is  devoted  to  general 
water  analysis,  and  the  microscopical  examination  of  water 

*  For  the  first  eight  years  of  its  existence  it  was  conducted  by  the 
author  under  the  general  direction  of  Mr.  Desmond  FitzGerald,  Super- 
intendent of  the  Western  Division  of  the  Water  Works. 


HISTORICAL.  3 

from  the  different  sources  of  supply  forms  an  important 
part  of  the  routine  work.  After  Brooklyn  became  a  part  of 
Greater  New  York,  in  1898,  the  work  of  this  laboratory  was 
extended  to  cover  all  the  water-supplies  of  the  city,  and 
branch  laboratories  were  established  on  the  Croton  and  Ridge- 
wood  watersheds.* 

Similar  biological  work  has  been  lately  undertaken  by 
health  boards  and  water  departments  and  by  sanitary  experts 
in  other  parts  of  the  country. 

The  reports  of  the  various  laboratories  show  that  during 
the  last  fifteen  years  about  one  hundred  thousand  samples  of 
water  have  been  submitted  to  microscopical  examination  in 
the  United  States,  and  that  this  number  is  increasing  at  ti.e 
rate  of  about  twelve  thousand  a  year. 

The  method  of  microscopical  examination  first  used  by 
the  Massachusetts  State  Board  of  Health  was  that  suggested 
by  Mr.  G.  H.  Parker.  A  piece  of  cotton  cloth  was  tied 
firmly  over  the  end  of  a  glass  funnel  and  200  c.c.  of  the  sam- 
ple were  made  to  pass  through  it.  The  organisms  were  left 
as  a  deposit  on  the  cloth.  After  this  straining  the  cloth 
was  removed  and  inverted  over  an  ordinary  microscopical 
slip.  The  organisms,  together  with  a  small  quantity  of 
water,  were  dislodged  upon  the  slip  by  blowing  downwards 
upon  the  cloth  through  a  piece  of  glass  tube.  This  method 
was  useful,  but  it  did  not  give  accurate  quantitative  results. 
Mr.  F.  F.  Forbes  of  Brookline,  Mass.,  used  a  modification 
of  the  cloth  method.  The  water  was  filtered  as  in  Parker's 
method,  but  the  neck  of  the  funnel  passed  into  a  tank  from 
which  the  air  was  exhausted  by  an  aspirator.  This  hastened 


*  From   1897  to  1904  these  laboratories  were  under  the  direction  of  the 
author. 


4  THE  MICROSCOPY   OF  DRINKING-WATER. 

the  filtration  and  allowed  a  larger  amount  of  water  to  be 
filtered. 

The  present  method  of  examination  was  foreshadowed  in 
the  work  of  Mr.  A.  L.  Kean.  He  filtered  100  c.c.  of  his 
samples  through  a  small  quantity  of  coarse  sand  placed  at  the 
bottom  of  a  glass  funnel  and  supported  by  a  plug  of  wire 
gauze.  After  filtration  the  plug  was  removed  and  the  sand 
with  its  contained  organisms  was  washed  into  a  watch-glass 
with  I  c.c.  of  water.  This  was  stirred  up  to  separate  the 
organisms  from  the  sand  and  a  portion  was  transferred  to  a 
cell  holding  one  cubic  millimeter.  From  the  number  of 
organisms  found  in  this  cell  the  approximate  number  orig- 
inally present  in  the  water  could  be  obtained.  This  method 
has  become  known  as  the  "  sand  method." 

In  1889  Prof.  Wm.  T.  Sedgwick  and  Mr.  Geo.  W.  Rafter 
made  valuable  improvements  upon  Kean's  original  idea. 
Prof.  Sedgwick  suggested  the  use  of  a  cell  much  larger  than 
that  used  by  Kean,  bounded  by  a  brass  rim  and  having  an 
area  of  1000  square  millimeters  ruled  by  a  dividing  engine  into 
1000  squares.  The  filtration  was  made  as  before,  and  the  sand 
was  washed  into  the  cell  with  one  or  two  cubic  centimeters  of 
water  and  distributed  over  the  bottom.  The  cell  was  then 
placed  under  the  microscope  and  the  organisms  counted  in  a 
certain  number  of  the  small  squares.  From  this  count  the 
number  of  organisms  present  in  the  sample  was  estimated. 
A  modification  of  this  method  was  the  one  first  used  by  the 
Connecticut  State  Board  of  Health.  In  the  Connecticut 
method  precipitated  silica  was  used  instead  of  sand  for  the 
filtering  medium,  and  this  was  supported  upon  a  pledget  of 
absorbent  cotton. 

Mr.  Rafter's  improvements  consisted  in  the  substitution 
of  a  ruled  square  in  the  ocular  of  the  microscope  for  the  ruling 


HISTORICAL.  5 

upon  the  plate,  in  the  separation  of  the  sand  from  the  organ- 
isms by  decantation,  in  the  use  of  a  cell  covered  by  a  cover- 
glass  and  containing  just  one  cubic  centimeter,  and  in  the  use 
of  a  specially  constructed  mechanical  stage.  The  Sedgwick- 
Rafter  method  has  been  modified  somewhat  by  recent  experi- 
menters,* but  its  essential  character  has  not  been  changed. 

While  sanitarians  have  been  pursuing  the  study  of  the 
microscopic  organisms  because  of  their  effect  on  the  quality 
of  water-supplies,  other  scientists  have  approached  the  subject 
from  an  entirely  different  standpoint.  In  the  same  year  that 
the  Massachusetts  State  Board  of  Health  began  its  examination 
of  the  water-supplies  of  the  State,  Victor  Hensen  of  the  Uni- 
versity of  Kiel,  Germany,  published  a  description  of  a  new 
method  of  studying  the  minute  floating  organisms  found  in, 
lakes.  To  these  organisms  he  gave  the  name  "  plankton,  f" 
a  collective  word  applied  to  all  minute  animals  and  plants 
that  float  free  in  the  water  and  that  are  drifted  about  by  waves 
and  currents.  Plants  attached  to  the  shore,  and  animals  that 
possess  strong  powers  of  locomotion,  are  not  included  in  the 
plankton,  but  fragments  of  shore  plants,  fish-eggs,  young  fish- 
fry,  etc.,  are  included.  The  term  4<  plankton,"  however, 
may  be  said  to  be  practically  synonymous  with  the  term, 
"microscopic  organisms"  of  the  sanitary  biologist. 


*  Dr.  Gary  N.  Calkins  substituted  a  perforated  rubber  stopper  capped 
by  a  circle  of  bolting-cloth  in  place  of  the  plug  of  wire  gauze.  Mr.  D.  D. 
Jackson  suggested  a  cylindrical  funnel  in  place  of  the  ordinary  flaring 
chemical  funnel,  and  added  an  attachment  at  the  lower  end  to  control  the 
concentration  and  prevent  the  sand  from  becoming  dry.  The  author  has 
graduated  the  funnels,  designed  a  simple  automatic  concentrating  device, 
and  applied  an  aspirator  to  hasten  the  filtration.  He  also  designed  the  ocu- 
lar micrometer  and  the  record  blank  now  used,  and  suggested  the  idea  of  a 
standard  unit  of  size  for  estimating  the  organisms  and  amorphous  matter. 

\  From  the  Greek  planktos,  wandering. 


6  THE   MICROSCOPY   OF  DRINKING-WATER. 

Hensen's  method  is  radically  different  from  the  Sedgwick- 
Rafter  method.  The  latter  is  strictly  a  laboratory  process. 
The  samples  of  water  operated  on  are  small;  the  concentra- 
tion of  the  organisms  is  made  in  the  laboratory.  Hensen 
devised  a  net  by  which  the  organisms  could  be  concentrated 
in  the  field,  so  that  only  the  collected  material  need  be  taken  to 
the  laboratory. 

Even  before  the  publication  of  Hensen's  paper,  scientists 
on  the  Continent  had  become  interested  in  the  study  of  lakes. 
The  early  observations  of  Prof.  F.  A.  Forel,  of  Morges,  Switzer- 
land, on  Lake  Geneva  were  followed  by  the  establishment  of  a 
Limnological  Commission  in  Switzerland.  Under  its  direction 
many  valuable  lines  of  physical  and  biological  research  were 
undertaken.  This  was  followed  in  1890  by  an  International 
Commission.  From  this  time  increased  attention  has  been 
given  to  the  biology  of  ponds  and  lakes.  A  biological  station  was 
established  by  Zacharias  at  Lake  Plon  in  1891,  and  a  group 
of  scientists  have  contributed  important  articles  to  its  annual 
reports.  Apstein  at  Kiel,  Schroeter  at  Zurich,  and  many  others 
have  made  extensive  and  valuable  observations.  Biological  stations 
have  multiplied  during  recent  years,  and  the  work  is  being  extended 
to  France,  Italy,  Austria,  Denmark,  Norway,  and  other  countries. 

Similar  investigations  have  been  carried  on  in  the  United  States. 
In  1893  Prof.  J.  E.  Reighard,  acting  under  the  direction  of  the 
Michigan  Fish  Commission,  made  a  biological  study  of  Lake 
St.  Clair.  This  was  followed  by  an  examination  of  Lake  Michi- 
gan by  Prof.  Henry  B.  Ward,  and  by  studies  of  the  Crustacea  in 
Lake  Mendota  by  Prof.  E.  A.  Birge,  and  in  Green  Lake  by 
Prof.  C.  Dwight  Marsh. 

Biological  stations  have  been  recently  established  by  a  number 
of  western  universities  on  or  in  the  vicinity  of  the  Great  Lakes, 
and  on  the  shores  of  smaller  bodies  of  water. 


HISTORICAL.  7 

Summer-school  courses  in  planktology  and  general  micro- 
scopic ecology  are  given  at  these  stations.  In  1900  an  American 
Limnological  Commission  *  was  organized  for  the  purpose  of 
stimulating  scientific  work  along  the  various  lines  of  natural 
science  involved,  and  of  co-ordinating  the  work  of  various  indi- 
viduals and  institutions.  This  commission  has  not  yet  made  a 
final  report. 

For  several  years  the  late  Prof.  James  I.  Peck,  acting  under 
the  direction  of  the  U.  S.  Fish  Commission,  made  important 
studies  of  the  food  of  certain  fishes,  notably  the  menhaden.  He 
used  the  Sedgwick- Rafter  method  instead  of  the  plankton  net  for 
concentrating  the  microscopic  organisms. 

In  1896  Dr.  C.  S.  Dolley,  of  Philadelphia,  suggested  the  use 
of  the  centrifugal  machine  for  the  purpose  of  concentrating  the 
microscopic  organisms.  This  "planktonokrit,"  as  it  is  called, 
lias  not  been  developed  to  completeness,  but  experiments  by 
Field,  Kofoid,  and  others  showed  that  it  is  likely  to  prove  of 
some  value. 

Prof.  H.  B.  Ward  and  Mr.  Chas.  Fordyce  devised  a  "  plank- 
ton pump"  for  collecting  Crustacea  and  other  plankton  organ- 
isms at  particular  depths  below  the  surface  of  a  lake.  In  many 
ways  this  was  a  decided  improvement  over  the  plankton  net. 

These  special  methods  have  more  value  for  strictly  scientific 
studies  of  the  organisms  than  for  the  practical  uses  of  the  water 
analyst  or  the  sanitary  expert. 


*  Consisting   of   Dr.  E.  A.  Birge,  Dr.  H.  B.  Ward,  Dr.  Charles    A.  Kofoh.1 
Dr.  C.  H.  Eigenmen,  and  G.  C.  Whipple. 


CHAPTER  II. 

THE    OBJECT  OF  THE  MICROSCOPICAL   EXAMINATION. 

A  COMPLETE  sanitary  examination  of  water,  as  conducted 
in  modern  laboratories,  consists  of  four  parts, — the  physical,  the 
microscopical,  the  bacteriological,  and  the  chemical.  The  data 
obtained  are  as  follows: 

PHYSICAL  EXAMINATION. 

Temperature — Turbidity — Color — Odor,    (both   cold    and 
hot). 

MICROSCOPICAL  EXAMINATION. 

Number  of  microscopic  organisms  per  c.c. — Amount  of 
inorganic  matter,  amorphous  matter,  etc. 

BACTERIOLOGICAL  EXAMINATION. 

Number  of  bacteria  per  c.c. — Presence  of  intestinal  bac- 
teria or  others  associated  with  pollution. 

CHEMICAL  EXAMINATION. 

Total  Residue  on  Evaporation — Loss  on  Ignition — Fixed 
Solids  —  Alkalinity  —  Hardness  —  Chlorine  —  Iron  — 
Nitrogen  as  Albuminoid  Ammonia — Nitrogen  as  Free 
Ammonia — Nitrogen  as  Nitrites — Nitrogen  as  Nitrates 
-  Total  Organic  Nitrogen  (Kjeldahl  Method)  - 
Oxygen  consumed — Dissolved  Oxygen — Free  Carbonic 
Acid,  etc.  (Some  of  these  are  of  use  only  in  special 

cases.) 

8 


THE    OBJECT   OF   THE   MICROSCOPICAL   EXAMINATION.         9 

Such  an  analysis  is  intended  to  show  whether  or  not  the 
water  is  of  such  a  character  that  it  would  cause  sickness  if 
used  for  drinking;  whether  or  not  it  contains  anything  that 
would  render  it  distasteful  or  unpalatable;  and  whether  or 
not  it  contains  any  ingredient  that  would  make  it  unfit  for 
laundry  use  or  for  general  domestic  or  industrial  purposes. 
Sanitary  examinations  are  necessary  also  in  studying  the 
effect  of  processes  of  purification. 

Opinions  regarding  the  function  and  value  of  sanitary 
water  analyses  have  undergone  a  change  in  recent  years. 
The  numerical  results  of  a  single  analysis  of  a  sample  of  water, 
when  considered  by  themselves,  are  now  believed  to  have 
little  intrinsic  value.  It  has  been  found  that  the  value  of  the 
analysis  lies  in  its  interpretation,  and  that  each  part  of  the 
analysis  must  be  interpreted  by  comparison  with  all  the  other 
parts  and  in  the  light  of  exact  knowledge  of  the  environment 
of  the  water.  The  interpretation  of  an  analysis  is  as  much  a 
matter  of  expert  skill  as  is  the  making  of  the  analysis  itself. 
The  physical,  biological,  and  chemical  examinations  should 
be  interlocking  in  their  testimony,  yet  these  different  parts 
are  to  be  given  different  weight  in  the  study  of  different 
problems.  For  example,  in  the  detection  of  pollution  the 
chemical  and  bacterial  examinations  furnish  the  most  infor- 
mation, in  the  study  of  the  aesthetic  qualities  of  a  water  the 
physical  and  microscopical  examinations  are  most  important, 
while  in  investigations  concerning  the  value  of  a  water  for 
industrial  purposes  the  chemical  and  physical  examinations 
may  alone  suffice. 

The  biological  examination  is  concerned  with  the  micro- 
organisms found  in  water.  The  term  "  micro-organisms," 
when  used  in  its  broadest  and  most  literal  significance,  includes 
all  organisms  which  are  invisible  or  barely  visible  to  the 


10 


THE   MICROSCOPY   Of   DRINKING-WATER. 


naked  eye.  It  is  frequently  used  in  a  narrower  sense,  how- 
ever, as  a  synonym  for  bacteria.  Using  the  word  in  its  broad 
sense  we  may  divide  the  micro-organisms  found  in  water 
into  two  classes,  as  suggested  by  Prof.  Sedgwick. 

Microscopic  Organisms. 


MICRO-ORGANISMS. 

Organisms,  either   plants   or  ^ 
animals,     invisible    or     barely 
visible  to  the  naked  eye. 


Not  requiring  special  culture. 
Easily  studied  with  the  microscope. 
Microscopic  in  size,  or  slightly  larger. 
Plants  or  animals. 

Bacteria  I  Orga  ms  ms.* 

Requiring  special  cultures. 
Difficultly  studied  with  the  microscope. 
Microscopic  or  sub-microscopic  in  size. 
Plants. 


This  subdivision  is  convenient  for  the  sanitarian  as  well  as 
for  the  biologist,  because  the  two  classes  of  organisms  affect 
water  in  different  ways.  With  certain  reservations  it  may  be 
said  that  the  bacteria  make  a  water  unsafe,  the  microscopic 
organisms  make  it  unsavory. 

Microscopical  Examination. — The  microscopical  exam- 
ination of  water  may  be  considered  in  five  aspects:  i. 
As  indicating  sewage  contamination.  2.  As  explaining 
the  chemical  analysis.  3.  As  explaining  the  cause  of  tur- 
bidity, odors,  etc.,  in  water.  4.  As  a  means  of  identifying 
the  source  of  a  water  (in  special  cases).  5.  As  a  method  of 
studying  the  food  of  fishes  and  other  aquatic  animals. 

I.   The    microscopical    examination     cannot   be   depended 
upon  to  determine  the  pathogenic  qualities    of   a    drinking- 


*  The  bacteria  are  not  considered  in  this  volume.     The  reader  is  referred  to 
the  numerous  works  on  Bacteriology  listed  in  the  bibliography  in  Appendix  C. 


THE    OBJECT   OF   THE   MICROSCOPICAL   EXAMINATION.       II 

water.  To  be  sure,  the  germs  of  disease  are  microscopic 
bodies,  and  when  artificially  cultivated  or  when  found  in 
the  tissues  of  the  body  they  can  be  studied  with  microscopes 
of  high  power.  But  when  scattered  through  a  mass  of 
water  they  cannot  be  detected  by  ordinary  microscopical 
methods,  because  of  their  small  size  and  because  they  are 
greatly  outnumbered  by  the  ordinary  water  bacteria.  It  is 
questionable  whether  they  can  be  discovered  even  by  methods 
of  culture.  Not  only  may  water  contain  pathogenic  bacteria 
without  discovery,  it  may  contain  the  ova  or  larvae  of  some 
•of  the  endoparasites  of  man.  It  is  probable  that  endoparasitic 
diseases  are  more  common  than  has  been  generally  supposed ; 
and  while  diseased  pork,  beef,  etc.,  are  the  chief  agencies  of 
infection,  it  is  known  that  water  polluted  by  animal  excrement 
may  contain  the  ova  or  larvae  of  such  endoparasites  as  Tcenia 
solium,  Tcenia  saginata,  Bothriocephalus  latus,  Ascaris  lumbri- 
coides,  Trichocephalus  dispar,  and  Anchylostomum  duodenale. 
Infection  of  animals  by  the  drinking  of  water  contaminated 
by  barnyard  wastes  has  been  several  times  recorded,  while  a 
microscopical  examination  of  the  water  has  seldom  revealed 
the  presence  of  the  suspected  ova  or  larvae.  This  is  not 
because  they  are  too  minute  to  be  detected,  but  because  the 
quantity  of  water  examined  is  necessarily  too  small. 

The  microscopical  examination  cannot  show  definitely 
whether  a  water  is  polluted  by  sewage  unless  the  pollution  is 
excessive.  It  can,  however,  give  evidence  which,  taken 
with  the  chemical  and  bacterial  examinations,  may  establish 
the  proof.  A  microscopical  examination  of  sewage  reveals 
few  of  the  living  organisms  that  are  found  ordinarily  in 
water.  Ciliated  infusoria,  such  as  Paramaecium  and  Trache- 
locerca;  fungus  forms,  such  as  mold  hyphae,  Saprolegnia, 
JLeptomitus,  Leptothrix,  and  Beggiatoa;  and  miscellaneous 


12  THE   MICROSCOPY   OF  DRINKING-WATER. 

objects,  such  as  yeast-cells,  starch-grains,  fibres  of  wood  and 
paper,  fibres  of  muscle,  epithelial  cells,  threads  of  silk,  woolen, 
cotton  and  linen,  insect  scales,  feather  barbs,  etc.,  may  be 
observed.  Most  of  these  objects  are  foreign  to  unpolluted 
water,  and  their  presence  in  a  sample  of  water  leads  one  to 
suspect  its  purity. 

Furthermore,  there  are  other  organisms,  such  as  Euglena 
viridis,  which  live  on  decaying  vegetable  matter  and  which, 
though  not  found  in  sewage,  are  often  associated  with  it 
in  polluted  water.  Their  presence  in  a  sample  is  a  cause 
of  suspicion.  These  evidences,  however,  should  be  weighed 
only  in  connection  with  an  environmental  study  and  with 
the  entire  sanitary  analysis.  The  common  microscopic  or- 
ganisms found  in  water  are  not  themselves  the  cause  of 
disease,  nor  does  their  presence  indicate  sewage  pollution. 

2.  The  chemical  examination  determines  the  amount  of 
organic  matter  that  a  sample  of  water  contains,  but  it  does  not 
determine  the  nature  of  it.  As  the  character  and  condition 
of  the  organic  matter  is  very  important  from  the  sanitary 
point  of  view,  the  microscopical  examination  gives  valuable  in- 
formation by  showing  not  only  whether  the  organic  matter  in 
suspension  is  vegetable  or  animal,  but  by  determining  whether 
it  is  made  up  of  living  organisms  or  of  decomposing  frag- 
ments. For  example,  the  amount  of  albuminoid  ammonia  in 
suspension  is  sometimes  so  great  that  one  might  suspect  that 
the  water  was  polluted  did  the  microscope  not  show  that  the 
high  figure  was  due  to  a  growth  of  some  organism.  Or  in  a 
series  of  samples  from  a  reservoir  it  might  be  difficult 
to  account  for  a  sudden  decrease  in  the  nitrates  or  free  am- 
monia were  it  not  for  the  appearance  of  some  microscopic 
organism  that  had  appropriated  the  nitrogen  as  a  part  of  its 
food. 


THE   OBJECT  OF   THE   MICROSCOPICAL   EXAMINATION.       1 3 

3.  By   far   the   most   important   service    that   the   micro- 
scopical examination  renders  is  that  of  explaining  the  cause 
of  the  taste  and  odor  of  a  water  and  of  its  color,  turbidity, 
and   sediment.      Several  of   the   microscopic   organisms  give 
rise  to  objectionable  odors  in  water  and,   when   sufficiently 
abundant,  have  a  marked  influence  on  its  color.      They  also 
make  the  water  turbid  and  cause  unsightly  scums  and  sedi- 
ments to  form.      Upon  all  such  matters  related  to  the  aesthetic 
qualities  of  a  water  the  microscopical  examination  is  almost 
the  only  means  of  obtaining  reliable  information. 

4.  The  presence  of  certain  microscopic  organisms  in  water 
sometimes  gives  a  clue  to  its  origin.    In  this  way  the  presence 
of  surface-water  in  a  well  may  be  detected.     In  the  Chicago 
Drainage  Canal  case  the  presence  of  Lake  Michigan  water  in 
the   St.    Louis  water-supply   was   indicated   by  finding   in  it 
certain  diatom  characteristics  of  the  Lake  Michigan  water. 

5.  The  microscopic  organisms  form  the  basis  of  the  food- 
supply  of   fish   and   other   aquatic   animals.      Sometimes   the 
relation  is  a  direct  one;  that  is,  the  microscopic  organisms  are 
themselves   eaten    by  fish.      This  was  well   illustrated   by   the 
late    Prof.    Peck.       The    menhaden     swims    with    its    mouth 
open,  and  is  provided  with  a  peculiar  filtering  apparatus   by 
which   the   minute   organisms  are   caught.      It  was  found  that 
the  presence  or  absence  of  these  fish  from  certain  sections  of 
the    Massachusetts    coast    depends  upon   the    abundance    of 
microscopic  life  in  the  water,  and  also  that  the  weight  of  fish 
of  any  particular  length  depends  upon  the  quantity  of  this 
food  material  at  hand. 

The  relationship  between  the  plankton  and  fish  life  is  not 
always  so  direct.  In  many  cases  the  fish  feed  upon  Crustacea 
and  insect  larvae;  the  Crustacea  feed  upon  the  rotifera  and 
protozoa;  the  rotifera  and  protozoa  feed  upon  algae;  while 


H  THE   MICROSCOPY   OF  DRINKING-WATER. 

the  algae  nourish  themselves  by  the  absorption  of  soluble  in- 
organic substances. 

The  interrelations  between  different  organisms  of  the 
lower  world,  and  between  the  organisms  and  their  environ- 
ment are  matters  of  intense  scientific  interest,  and  limnology 
and  microscopical  ecology  are  fast  assuming  important  places 
in  scientific  literature.  The  physical  condition  of  lakes,  the 
currents,  waves,  temperature,  and  transparency  of  water,  the 
chemistry  of  water,  the  life-history  of  organisms,  and  various 
bio-chemical  and  bio-physical  problems  are  more  and  more 
attracting  the  attention  of  scientists  and  of  water-works 
engineers. 


CHAPTER    III. 
METHODS   OF   MICROSCOPICAL  EXAMINATION. 

THE  most  important  methods  of  microscopical  examina- 
tion of  water  now  in  use  are:.  I.  The  Sedgwick-Rafter 
Method;  2.  The  Plankton  Net  Method;  3.  The  Plankton 
Pump  Method;  4.  The  Planktonokrit.  They  differ  chiefly 
in  the  manner  of  concentrating  the  organisms. 

I.  THE  SEDGWICK-RAFTER  METHOD. 

^ 

The  Sedgwick-Rafter  Method  consists  of  the  following 
processes:  the  filtration  of  a  measured  quantity  of  "the  sample 
through  a  layer  of  sand  upon  which  the  organisms  are  de- 
tained; the  separation  of  the  organisms  from  the  sand  by 
washing  with  a  small  measured  quantity  of  filtered  or  dis- 
tilled water  and  by  decanting;  the  microscopical  examination 
of  a  portion  of  the  decanted  fluid;  the  enumeration  of  the 
organisms  found  therein;  and  the  calculation  from  this  of  the 
number  of  organisms  in  the  sample  of  water  examined.  The 
essential  parts  of  the  apparatus  are  the  filter,  the  decanta- 
tion-tubes,  the  cell,  and  the  microscope  with  an  ocular  mi- 
crometer. 

The  Filter. — The  sand  may  be  supported  upon  a  plug  of 
rolled  wire  gauze  at  the  bottom  of  an  ordinary  glass  funnel  7 
or  8  inches  in  diameter,  but  the  cylindrical  funnel  shown  in 
Fig.  I  is  preferable.  The  inside  diameter  of  this  funnel  at 

15 


i6 


THE   MICROSCOPY   OF  DRINKING-WATER. 


c.c, 
500 


450 


400 


350 


300 


250 


200 


150 


100 


the  top  is  2  inches;  the  distance  from  the  top  to  the  begin- 
ning of  the  slope  is  9  inches;  the  length  of  the  slope  is  about 
3  inches;  the  length  of  the  tube  of  small  bore  is  2^  inches,  and 
its  inside  diameter  is  J  inch.  The  capacity  of 
the  funnel  is  500  c.c.  The  support  for  the  sand 
consists  of  a  perforated  rubber  stopper  pressed 
tightly  into  the  stem  of  the  funnel  and  capped 
with  a  circle  of  fine  silk  bolting-cloth.  The 
circles  of  bolting-cloth  may  be  cut  out  with  a 
wad-cutter.  Their  diameter  should  be  a  little 
less  than  that  of  the  small  end  of  the  rubber 
stopper.  When  moist  the  cloth  readily  adheres 
to  the  stopper.  The  sand  resting  upon  the 
platform  thus  prepared  should  have  a  depth  of 
at  least  three  fourths  of  an  inch.  The  quality 
of  the  sand  is  important.  Ordinary  sand  is 
unsatisfactory  unless  very  thoroughly  washed. 
Pure  ground  quartz  is  preferable.  Its  whiteness 
is  a  decided  advantage.  The  necessary  degree 
of  fineness  of  the  sand  depends  somewhat  upon 
the  character  of  the  water  to  be  filtered.  A 
sand  which  will  pass  through  a  sieve  having  60 
meshes  to  an  inch,  but  which  will  be  retained 
by  a  sieve  having  120  meshes,  will  be  found 
satisfactory  for  most  samples.  Such  a  sand  is 
UATED  CYLIN-  Described  as  a  60-120  sand.  When  very  mi- 
DRICAL  FUN-  nute  organisms  are  present  a  finer  sand  must  be 

NEL   USED  IN  used       say  a  6o~i4O  sand.     The  sand  used  for 

THE       SEDG-  J 

WICK- RAFTER  many   years   by  the   author  had    the    following 

METHOD-         composition: 

Size  of  sand-grains 40-60       60-80       80-100       100-120       120-140 

Percentage  by  weight. .     20  20  38  18  4        =  100 


f 
FIG.  i. — GRAD- 


METHODS   OF  MICROSCOPICAL   EXAMINATION.  I/ 

The  filters  may  be  arranged  conveniently  in  a  row  against 
the  laboratory  wall  as  shown  in  Fig.  2.      The  filtered  water 


FIG.  2. — BATTERY  OF  FILTERS.     SEDGWICK-RAFTER  METHOD. 

may  be  collected  in  a  sloping  trough  and  carried  to  a  sink, 
or  jars  may  be  placed  under  the  separate  funnels.  A  hinged 
covering-shelf  above  the  filters  is  useful  to  prevent  the  access 
of  dust. 

The  sample  to  be  filtered  may  be  measured  in  a  graduated 
cylinder  or  flask,  or  the  filter-funnel  itself  may  be  graduated. 
The  graduated  filter-funnel  is  especially  useful  for  field  work, 
as  it  saves  the  necessity  of  carrying  an  additional  graduate. 
The  quantity  of  water  that  should  be  filtered  depends  upon 
the  number  of  organisms  and  the  amount  of  amorphous 


1 8  THE   MICROSCOPY   OF  DRINKING-WATER. 

matter  present.  An  inspection  of  the  sample  will  enable  one 
to  judge  the  proper  amount.  Ordinarily  1000  c.c.  for  a 
ground-water  and  500  c.c,  for  a  surface-water  will  be  found 
satisfactory.  In  some  cases  250  c.c.  or  even  100  c.c.  of  a 
surface-water  will  be  found  more  convenient.  When  the 
water  is  poured  into  the  funnel  care  should  be  taken  not  to 
disturb  the  sand  more  than  is  necessary,  otherwise  organ- 
isms are  liable  to  be  forced  through  the  filter.  The  best 
plan  is  to  make  the  sand  compact  by  pouring  in  enough 
distilled  water  to  just  about  fill  the  neck  of  the  funnel  and  to 
pour  in  the  measured  sample  before  the  sand  has  become 
uncovered.  The  filtration  ordinarily  takes  place  in  about 
half  an  hour,  but  occasionally  a  sample  is  so  rich  in  organisms 
and  amorphous  matter  that  the  filter  becomes  clogged.  It 
then  becomes  necessary  to  agitate  the  sand  with  a  glass  rod 
or  to  apply  a  suction  to  hasten  the  filtration.  If  the  filters 
are  located  near  running  water  an  aspirator  may  be  attached 
to  the  faucet  and  connected  with  the  filter  by  a  rubber  tube 
having  a  glass  connection  that  fits  the  bore  of  the  rubber 
stopper.  The  use  of  the  aspirator  enables  the  filtration  to  be 
made  in  a  few  minutes,  and  not  only  effects  a  saving  in  time, 
but  reduces  the  error  caused  by  the  organisms  settling  on  the 
sloping  surface  of  the  funnel. 

Concentration. — As  a  result  of  the  filtration  the  organ- 
isms and  whatever  other  suspended  matter  the  sample  con- 
tained will  have  been  collected  on  the  sand.  When  all  the 
water  has  passed  through  and  before  the  sand  has  become  dry 
the  rubber  stopper  is  removed  and  the  sand  with  its  accumu- 
lated organisms  is  washed  down  into  a  wide  test-tube  by  a 
measured  quantity  of  filtered  or  distilled  water  delivered  from 
a  pipette  or  an  automatic  burette.  The  amount  of  water 
used  for  washing  depends  upon  the  number  of  organisms 


ME7^HODS   OF  MICROSCOPICAL   EXAMINATION. 


collected  on  the  sand.  If  500  c.c.  of  the  sample  are  filtered 
it  is  usually  best  to  wash  the  sand  with  5  c.c.,  thus  concen- 
trating the  organisms  one  hundred  times.  The  amount  of 
water  filtered  divided  by  the  amount  of  water  used  in  wash- 
ing the  sand  gives  the  "  degree  of  concentration."  The 
degree  of  concentration  may  vary  from  10 
to  500  according  to  the  contents  of  the 
sample.  Ordinarily  it  should  be  50  or  100. 

By  shaking  the  tes.t-tube  the  organisms 
will  become  detached  from  the  sand-grains. 
If  this  is  followed  by  a  rapid  decantation  into 
a  second  test-tube  most  of  the  organisms, 
being  lighter  than  the  sand,  will  pass  over 
with  the  decanted  fluid,  while  the  sand  is 
left  upon  the  walls  of  the  first  tube.  To 
insure  accuracy  the  sand  should  be  washed 
a  second  time  and  the  two  decanted  por- 
tions mixed  together.  If,  for  example,  it 
is  desired  to  concentrate  a  sample  from 
500  c.c.  to  10  c.c.  the  sand  should  be 
washed  twice  with  5  c.c.  and  the  two  por- 
tions poured  together.  This  will  give  a 
more  accurate  result  than  a  single  washing 
with  10  c.c. 

Mr.  D.  D.  Jackson  has  suggested  the 
use  of  an  attachment  at  the  lower  end  of 
tne  funnel  that  automatically  arrests  the 
filtration  as  soon  as  the  proper  degree  of 
concentration  has  been  reached.  This  is 
illustrated  in  Fig.  3.  The  attachment  fits 
over  the  rubber  cork  that  supports  the  sand,  uniting  with  the 
lower  end  of  the  neck  of  the  filter  by  a  ground  joint.  The 


FIG.  3.  —  CONCEN- 
TRATING ATTACH 
MENT.  SEDGWICK- 
RAFTER  METHOD. 


20 


THE   MICRO  SCOP  Y  OF  DRINKING-  IV A  TER. 


filtered  water  passes  out  of  the  open  tube,  and  filtration 
stops  as  soon  as  the  level  of  the  water  in  the  funnel  has 
reached  the  elevation  of  the  outlet-tube.  This  elevation  is 
made  such  that  the  water  remaining  in  the  neck  of  the  funnel 
is  just  sufficient  to  give  the  desired  degree  of  concentration. 
It  is  necessary  to  allow  for  the  volume  of  the  sand  and  to  use 
a  definite  amount  of  sand  at  each  filtration.  The  60-120 
sandl  holds  about  50$  of  water,  and  ordinarily  about  2  c.c.  of 
the  sjand  are  used;  hence  an  allowance  of  i  c.c.  must  be  made 
for  tpe  water  held  in  the  sand.  Thus,  if  it  is  desired  to  con- 
centrate the  organisms  in  5  c.c.  of 
water,  the  capacity  from  the  bottom 
of  the  sand  layer  to  the  graduation 
on  the  stem  of  the  funnel  must  be  6 
c.c.,  i.e.  4  c.c.  above  the  2  c.c.  of 
sand.  After  filtration  the  attachment 
is  removed  and  a  plug  is  inserted  in 
the  hole  in  the  stopper  to  prevent  loss 
of  the  concentrated  fluid.  The  stop- 
per then  may  be  removed  and  the  sand 
and  organisms  allowed  to  fall  into  a 
wide  test-tube,  after  which  the  pro- 
cess is  carried  on  as  described  below. 
The  same  result  has  been  accom- 
plished by  the  author  in  a  simpler 
way.  In  place  of  the  attachment  with 

the  ground-glass  joint  a  glass  tube 
FIG.  4.  —  SIMPLE  FORM  OF 

•  CONCENTRATING   ATTACH- bent  twice  at  right  angles  may  be  in- 

•  MENT.   SEDGWICK-RAFTER  serted  in  the  opening  in  the  rubber 
METHOD.  .      T,.  r~.      e 

stopper  as  shown  in  Fig. 4.  The  fun- 
nel stem  may  be  graduated  and  a  series  of  bent  tubes  pro- 
vid.ed  corresponding  to  different  degrees  of  concentration. 


^ 

f 

C.C. 

i 

-  5  - 

— 

-  4  - 

\ 

\ 

-  3  - 

• 

1 

-  2  - 

lee 
ftoUa 

V 
.  of  »and  _____ 
Ice.  of  water 

if 

____-X 

METHODS   OF  MICROSCOPICAL   EXAMINATION.  21 

If  the  operator  is  watching  the  filtration  even  this  form  of 
attachment  is  unnecessary,  as  the  filtration  may  be  stopped 
by  inserting  a  plug  in  the  rubber  stopper  as  soon  as  the  level 
of  the  water  has  fallen  to  the  desired  point.  This  method 
of  concentrating  is  to  be  preferred  to  the  usual  one  described 
above  in  which  the  surface  of  the  sand  is  allowed  to  become 
uncovered  before  the  sand  is  washed  into  the  test-tube. 
As  the  use  of  either  form  of  attachment  described  above 
retards  the  rate  of  filtration  it  is  better  not  to  put  on  the 
attachment  until  the  water  has  fallen  almost  to  the  desired 
level. 

If  the  concentrated  water  is  allowed  to  stand  in  the  funnel 
for  any  length  of  time  some  of  the  organisms  are  liable  to 
become  attached  to  the  glass  sides.  To  prevent  error  from 
this  cause  the  neck  of  the  funnel  may  be  washed  with  a  small 
measured  quantity  of  filtered  water,  and  this  may  be  caught 
in  the  large  test-tube  and  used  for  washing  the  sand  a  second 
time  as  described  above. 

The  Cell. — The  cell  into  which  a  measured  portion  of  the 
concentrated  fluid  is  placed  for  examination  is  made  by 
cementing  a  rectangular  brass  rim  to  an  ordinary  glass  slip. 
The  internal  dimensions  of  the  cell  are:  length  50  mm.,  width 
20  mm.,  and  depth  I  mm.  It  therefore  has  an  area  of  1000 
sq.  mm.  and  a  capacity  of  I  c.c.  A  thick  cover-glass  (No.  3) 
having  dimensions  equal  to  those  of  the  outside  of  the  brass 
rim  (55  mm.  by  25  mm.)  forms  a  roof  to  the  cell.  The  con- 
centrated organisms  in  the  decantation-tube  are  distributed 
uniformly  through  the  fluid  by  blowing  into  it  through  a 
pipette,  and  one  cubic  centimeter  of  the  fluid  is  then  trans- 
ferred to  the  cell  in  such  a  manner  as  to  distribute  the  organ- 
isms evenly  over  the  entire  area.  This  may  be  done  by  laying 
the  cover-glass  diagonally  over  the  cell  so  that  an  opening  is 


22 


THE   MICROSCOPY   OF  DRINKING-WATER, 


left  at  either  end,  and  flowing  the  water  in  at  one  end  while 
the  air  escapes  at  the  other  (see  Fig.  5). 


FIG.  5. — COUNTING-CELL,  SHOWING  METHOD  OF  FILLING.     SEDGWICK- 
RAFTER  METHOD. 

The  -Microscope. — An  expensive  microscope  is  not 
needed  for  the  numerical  estimation  of  the  common  micro- 
scopic organisms  found  in  water.  A  simple,  compact  stand 
with  a  J-inch  objective  and  a  i-inch  ocular  is  sufficient.  For 
studying  the  organisms  in  detail  and  for  general  laboratory  use 
in  the  study  of  water  a  large  stand,  with  substage  condenser, 
iris  diaphragm,  mechanical  stage,  etc.,  should  be  provided. 
The  list  of  objectives  should  include  a  2-inch,  a  ^-inch,  a  J- 
or  ^-inch,  and  a  T^-inch  homogeneous  immersion,  or  their 
equivalents,  and  there  should  be  several  oculars  magnifying 
from  4  to  12  times. 

The  ocular  micrometer  consists  of  a  square  ruled  upon  a 
thin  glass  disk  which  is  placed  upon  the  diaphragm  of  the 
ocular.  The  square  is  of  such  a  size  that  with  a  certain  com- 
bination of  objective  and  ocular  and  with  a  certain  tube-length 


METHODS   OF  MICROSCOPICAL   EXAMINATION.  2$ 

of  the  microscope,  the  area  covered  by  it  on  the  stage  is  just 
one  square  millimeter.  For  convenience  it  should  be  sub- 
divided as  shown  in  Fig.  6.  The  size  of  the  largest  square 
is  one  square  millimeter.  The  size  of  the  smallest  square  is 


FIG.  6. — OCULAR  MICROMETER  USED  IN  THE  SEDGWICK-RAFTER  METHOD. 
one  standard  unit.*  The  best  micrometers  are  made  by  en- 
graving, but  a  serviceable  micrometer  for  occasional  use  may 
be  made  by  photography. f  With  a  J-inch  objective  and  a 
No.  3  ocular  the  square  ruled  for  the  ocular  micrometer 
should  be  7  mm.  on  a  side.  Before  using  the  micrometer  the 
proper  tube-length  must  be  ascertained  by  comparison  with 
a  stage  micrometer. 

Enumeration. — The  x:ell,  filled  with  the  concentrated 
fluid,  is  placed  upon  the  stage  of  the  microscope  and  the 
organisms  included  within  the  area  of  the  ruled  square  are 
counted.  It  is  then  moved  so  that  another  portion  of  the 
comes  into  the  field  of  view  and  another  square  is  counted. 

*  See  page  29. 

•f-  This  idea  was  suggested  by  Mr.  Wallace  Goold  Levison,  Brooklyn,  N.  Y. 


24  THE   MICROSCOPY  OF  DRINKING-WATER. 

This  is  continued  until  a  sufficient  number  of  representative 
squares  has  been  examined.  It  is  obviously  impracticable  to 
count  all  of  the  1000  squares  which  compose  the  area  of  the 
cell.  It  is  usually  sufficient  to  count  ten  or  twenty  squares, 
but  a  larger  number  ought  to  be  scrutinized.  In  counting 
the  organisms  it  should  be  remembered  that  some  are  heavy 
and  sink  to  the  bottom,  while  others  are  light  and  rise  to  the 
top.  The  observer  should  make  a  practice  of  changing  the 
focus  of  the  microscope  so  that  both  the  upper  and  lower 
portions  of  each  square  may  be  examined. 

From  the  number  of  organisms  found  in  the  ten  or  twenty 
squares  it  is  an  easy  matter  to  calculate  the  number  originally 
present  in  one  cubic  centimeter  of  the  sample.  If  /  repre- 
sents the  mimber  of  organisms  found  in  twenty  squares, 
f 
• —  will  represent  the  number  found  in  one  square,  and 

5<D/f=  —  X  1000)   will  represent  the  number  in  the  entire 

cell,  or  in  one  cubic  centimeter  of  the  concentrated  fluid. 
This  divided  by  the  degree  of  concentration  will  give  the 
number  of  organisms  in  one  cubic  centimeter  of  the  sample. 
For  example,  if  the  sample  has  been  concentrated  from  500 
c.c.  to  5  c.c.  the  degree  of  concentration  will  be  100,  and 

therefore  =  \t  will  represent  the  "  number  of  organisms 

per  c.c."  in  the  sample.  The  figure  by  which  the  total 
number  of  organisms  counted  must  be  multiplied  in  order  to 
reduce  to  "number  per  c.c."  may  be  called  the  factor.  Its 
value  may  be  expressed  as  follows: 

IOOOW 

Factor  =  —^-, 
in  which  f  equals  the  number  of  cubic  centimeters  of  water 


METHODS   OF  MICROSCOPICAL   EXAMINATION.  2$ 

filtered;   «/,  the  number  of  cubic  centimeters  of  water  used  ia 
washing  the  sand ;  and  ny  the  number  of  squares  counted. 

Sources  of  Error. — The  operations  of  the  Sedgwick- 
Rafter  method  involve  several  sources  of  error.  They  may 
be  classified  as  follows: 

1.  Errors  in  sampling. 

2.  Funnel   error,   or  the   error  caused  by  the  organisms 
adhering  to  the  sides  of  the  funnel. 

3.  Sand  error,  or  the  error  caused  by  imperfect  filtration. 

4.  Error   of    disintegration,  due    to  the   breaking  up  of 
organisms  on  the  surface  of  the  sand. 

5.  Decantation  error,  or  the  error  caused  by  the  organ- 
isms adhering  to  the  particles  of  sand,  and  by  the  water  used 
in  washing  the  sand  being  held  back  by  capillarit^during  the 
process  of  decantation. 

6.  Errors  caused  by  the  organisms  not  being  uniformly 
distributed  in  the  cell. 

Errors  in  Sampling. — These  errors  arise  chiefly  from  the 
fact  that  organisms  vary  in  specific  gravity  and  in  their 
behavior  towards  light.  If  the  bottle  containing  the  sample 
is  allowed  to  stand  even  for  a  short  time,  some  of  the  organ- 
isms will  sink  to  the  bottom,  some  will  rise  to  the  surface ; 
some  will  collect  on  the  side  of  the  bottle  towards  the  light, 
others  will  shun  the  light  as  much  as  possible;  while  some  will 
attach  themselves  quite  firmly  to  the  sides  of  the  glass. 
Evidently  the  bottle  must  be  shaken  before  the  portion  for 
examination  is  withdrawn.  Errors  in  sampling  are  common, 
but,  to  a  great  extent,  are  avoidable. 

Funnel  Error. — The  funnel  error,  due  to  the  organisms 
settling  upon  and  adhering  to  the  sloping  sides  of  the  funnel, 
varies  greatly  according  to  the  character  of  the  water  filtered. 
It  is  highest  in  the  case  of  samples  rich  in  the  Cyanophyceae 


26  THE   MICROSCOPY   OF  DRINKING-WATER. 

and  amorphous  matter.  These,  being  of  a  somewhat  gelati- 
nous nature,  adhere  readily  to  the  glass,  making  a  rough 
surface  on  which  other  organisms  lodge.  If  the  funnel  is  wet 
when  the  sand  is  put  in,  some  of  the  sand-grains  are  liable  to 
adhere  to  the  sloping  walls.  This  tends  to  increase  the 
deposition  of  organisms.  The  funnel  error  is  less  in  the 
cylindrical  funnels  than  in  the  flaring  funnels.  Slow  filtra- 
tion, whether  due  to  the  character  of  the  funnel  or  to  the 
sample  filtered,  increases  the  error, — indeed  it  may  be  said 
that  the  funnel  error  is  almost  proportional  to  the  time  of 
filtration.  Numerically  the  funnel  error  may  vary  from  o  to 
15^.  A  long  series  of  experiments*  on  waters  that  varied 
greatly  in  character  gave  an  average  error  of  \<f>  for  the 
organisms  and  3$  for  the  amorphous  matter. 

Sand  Error. — The  sand  error,  due  to  imperfect  filtration, 
depends  upon  the  character  of  the  organisms,  upon  the  size 
of  the  sand-grains,  and  upon  the  depth  of  the  sand.  In 
selecting  a  sand  two  opposing  conditions  must  be  adjusted. 
The  sand  must  be  fine  enough  to  form  an  efficient  filter,  and 
yet  the  grains  must  be  large  enough  to  settle  readily  in  the 
decantation-tubes.  A  £-inch  layer  of  the  sand  described  on 
page  16  ought  not  to  give  a  sand  error  greater  than  5$  unless 
the  water  contains  minute  organisms.  When  very  minute  or- 
ganisms are  present  in  large  numbers  the  error  from  incomplete 
filtration  may  be  as  great  as  25$  or  even  50$.  The  effect  of 
the  size  of  the  sand-grains  on  the  sand  error  is  well  illustrated 
by  the  following  table  compiled  from  experiments  by  Calkins  on 
the  filtration  of  water  containing  yeast-cells  and  starch-grains: 

Percentage  Sand  Error. 
Size  of  Sand. 

Yeast-cells.  Starch-grams. 

40-60  21.6  4.4 

60-80  8.7  7  ..3 

80-100  5.3  7.4 

100-120  3.3  1.2 

*  By  the  author. 


METHODS   OF  MICROSCOPICAL    EXAMINATION.  2? 

Most  of  the  organisms  that  pass  through  the  sand  do  so 
'during  the  early  part  of  the  filtration,  belore  the  sand  has 
become  compacted.  If,  before  the  sample  is  pouted  into  the 
funnel,  the  sand  is  compacted  by  passing  through  it  some 
distilled  water,  using  the  aspirator  to  increase  the  pressure, 
the  sand  error  will  be  reduced  considerably. 

Errors  of  Disintegration.  —  Many  of  the  microscopic 
•organisms  are  extremely  delicate.  They  are  very  susceptible 
to  changed  conditions  of  temperature,  pressure,  and  light. 
As  soon  as  a  sample  of  water  has  been  collected  in  a  bottle 
some  of  the  organisms  begin  to  disintegrate;  and  if  the  sam- 
ple stands  long  before  examination  and  if  it  is  submitted  to 
the  joltings  of  a  long  trip  by  express,  some  of  the  organisms 
will  break  up  and  become  unrecognizable.  The  process  of 
filtration  helps  to  disintegrate  them  by  bringing  them  in 
violent  contact  with  the  surface  of  the  sand,  but  the  method 
of  concentrating  the  sample  by  arresting  the  filtration  as 
described  above  reduces  this  error  to  a  considerable  extent 
by  keeping  the  sand  from  becoming  dry  and  by  preventing 
many  of  the  organisms  from  even  reaching  the  surface  of  the 
^and.  The  errors  due  to  disintegration  during  transit  and 
-before  examination  can  be  avoided  only  by  making  the  exami- 
nation at  the  time  of  collection.  This  is  often  necessary, 
particularly  when  one  is  searching  for  such  delicate  organisms 
-as  Uroglena.  The  errors  of  disintegration  during  filtration 
cannot  be  entirely  avoided,  but  if  the  examination  of  the 
concentrated  fluid  is  supplemented  by  a  direct  examination 
cf  the  water  gross  mistakes  may  be  prevented.  Uroglena, 
Dinobryon,  etc.,  may  be  detected  in  the  sample  with  the 
naked  eye  after  a  little  practice.  They  may  be  taken  up 
with  a  pipette  and  transferred  to  the  stage  of  the  micro- 
.scope.  This  direct  examination  is  important  and  ought 


28  THE  MICROSCOP  Y   OF  DRINKING-  WA  TER. 

always  to  be  made,  but  its  value  is  qualitative  and  not 
quantitative. 

Decantation  Error. — The  decantation  error  depends  to  a 
great  extent  upon  care  in  manipulation.  When  the  attempt 
is  made  to  separate  the  organisms  from  the  sand  by  agitating 
with  distilled  water  in  one  test-tube  and  decanting  into  a 
second  tube,  some  of  the  organisms  remain  behind  attached 
to  the  sand-grains,  and,  what  is  quite  as  important,  some  of 
the  water  used  in  washing  remains  behind. 

The  two  errors  act  in  opposition.  If  the  sand  retains  a 
larger  percentage  of  organisms  than  of  water,  the  figures  in  the 
result  will  be  too  low;  if  it  retains  a  larger  percentage  of 
water  than  of  organisms,  the  concentration  will  be  too  great 
and  the  figures  in  the  result  will  be  too  high.  With  the  frac- 
tional method  of  washing  the  sand  and  with  due  care  in  de- 
canting the  decantation  error  ought  not  to  exceed  5  per  cent. 

Errors  in  the  Cell. — The  errors  due  to  the  unequal  distri- 
bution of  the  organisms  over  the  area  of  the  cell  are  extremely 
variable  and  cannot  be  well  stated  in  figures.  If  the  concen- 
trated fluid  is  evenly  mixed  and  well  distributed  over  the  cell, 
if  the  count  is  made  just  as  soon  as  the  material  in  the  cell 
has  settled,  and  if  a  large  number  of  squares  are  counted,  the 
error  will  be  reduced  to  a  minimum.  If  a  sample  happens  to- 
contain  such  motile  organisms  as  Trachelomonas  they  may 
collect  at  the  edges  of  the  cell  in  search  of  air,  or  if  the  cell 
stands  in  front  of  a  window  for  any  length  of  time  organisms 
sensitive  to  light  may  migrate  from  one  side  of  the  cell  to  the 
other. 

Precision  of  the  Sedgwick-Rafter  Method. — Examina- 
tion of  hundreds  of  samples  has  shown  that  the  results  are 
usually  precise  within  io#,  i.e.  two  examinations  of  the  same 
sample  seldom  differ  by  more  than  that  amount.  The 


METHODS   OF  MICROSCOPICAL   EXAMINATION.  29 

accuracy,  however,  depends  greatly  upon  the  character  of  the 
organisms  in  the  water  examined. 

Results  of  Examination — Standard  Unit. — The  micro- 
scopical examination  of  most  samples  of  surface-water  will 
show  that  the  concentrated  fluid  contains  minute  organisms 
of  various  kinds,  fragments  of  larger  animals  and  plants, 
masses  of  a  grayish  or  brownish  flocculent  material,  and  fine 
particles  of  inorganic  matter.  The  inorganic  or  mineral 
matter  is  usually  not  considered  in  the  Sedgwick-Rafter 
method;  more  information  can  be  obtained  by  a  direct 
examination  of  the  sediment  and  by  chemical  analysis.  The 
brownish  flocculent  material  has  been  called  "amorphous 
matter"  because  of  its  formless  nature,  and  "  zoogloea  " 
because  of  its  supposed  bacterial  origin.  The  term  zoogloea 
has  a  definite  meaning  in  bacteriology  and  is  applied  to  a  mass 
of  bacteria  held  together  by  a  more  or  less  transparent  gluti- 
nous substance.  It  is  not  strictly  appropriate  as  applied  to  the 
brownish  flocculent  matter,  which  is  not  so  much  a  collection 
of  bacteria  as  the  product  of  bacterial  action.  The  word 
phytoglcea  might  be  used  in  its  place,  but  the  term  "amor- 
phous matter"  is  a  broader  term  and  quite  as  appropriate. 
The  amorphous  matter,  then,  includes  all  the  irregular  masses 
of  unidentifiable  organic  matter.  It  does  not  include  vege- 
table fibres,  vegetable  tissue,  etc.,  nor  does  it  include  mineral 
matter  except  as  this  is  intimately  mixed  with  the  flocculent 
material.  The  amorphous  matter  occurs  in  a  finely  divided 
state  or  in  lumps  of  varying  size.  In  order  to  correctly 
estimate  its  amount  it  is  necessary  to  have  some  unit  of  size. 
A  unit  of  volume  is  impracticable  because  of  the  great  labor 
involved  in  determining  the  dimensions  of  the  masses 
observed,  but  a  unit  of  area  approaches  closely  to  what  is 
desired.  Such  a  unit  was  suggested  by  the  author  in  1889, 


30  THE   MICROSCOPY   OF  DRINKING-WATER. 

and  has  come  into  use  under  the  name  of  "standard  unit." 
The  standard  unit  is  represented  by  the  area  of  a  square 
2O  microns*  on  a  side,  i.e.  by  400  square  microns. 

The  ocular  micrometer  shown  in  Fig.  6  was  subdivided 
to  correspond  to  this  unit.  The  square,  which  covers  one 
square  millimeter  on  the  stage  of  the  microscope,  is  divided 
into  four  equal  squares.  Each  of  these  quarters  is  subdivided 
into  25  smaller  squares,  and  each  of  these  squares  contains  25 
standard  units.  The  eye  will  readily  divide  the  side  of  a 
small  square  into  fifths,  and  this  division  is  the  side  of  the 
standard  unit  square.  If  desired,  one  of  the  small  squares 
may  be  further  subdivided  into  squares  the  actual  size  of  the 
standard  unit  as  shown  in  the  figure.  This  can  be  done  on 
the  micrometers  made  by  photography,  but  not  conveniently 
on  those  engraved. 

The  microscopic  organisms  vary  in  size  and  in  their  mode 
of  occurrence.  Some  are  found  as  separate  individuals,  some 
are  joined  together  into  filaments,  or  into  masses  or  colonies; 
some  are  one-celled,  some  are  many-celled ;  some  are  extremely 
simple,  some  are  complex;  some  are  scarcely  larger  than  the 
bacteria,  some  are  easily  visible  to  the  naked  eye.  It  is 
difficult  to  establish  a  satisfactory  system  for  counting  these 
varied  forms.  If  an  individual  count  is  adopted  one  has  to 
decide  what  shall  be  the  unit,  whether  a  cell,  or  a  filament,  or 
a  colony,  or  a  mass.  Practice  has  varied  in  this  matter.  The 
best  system  of  counting  by  individuals  is  that  used  by  the 
Massachusetts  State  Board  of  Health.  All  diatoms,  desmids, 
rhizopods,  Crustacea,  the  unicellular  algae,  and  nearly  all 
rotifera  and  infusoria  are  counted  as  individuals;  the  filamen- 
tous algae  are  counted  as  filaments;  the  social  forms  of 
infusoria  and  rotifera  are  counted  as  colonies;  and  many  of 
the  algae  that  occur  as  irregular  thalli  are  counted  as  masses, 
*  One  micron  =  .001  millimeter. 


METHODS   OF  MICROSCOPICAL   EXAMINATION.  31 

This  system,  which,  for  convenience,  we  may  call  the  "in- 
dividual counting  system,"  does  not  always  give  satisfactory 
results.  In  the  Boston  water-supply  it  was  found  often  that 
a  sample  which  a  simple  inspection  showed  to  be  heavily  laden 
with  algae  and  which  was  offensive  both  in  appearance  and  in 
odor  gave  a  low  figure  in  the  count,  while  a  sample  that  was 
clear  and  agreeable  to  the  taste  gave  a  very  high  figure. 
This  was  due  largely  to  the  great  difference  in  the  size  of  the 
organisms.  A  great  mass  of  Clathrocystis  was  given  no  more 
weight  in  the  result  than  a  tiny  Cyclotella.  Each  counted 
one,  though  the  former  sometimes  contained  a  thousand  times 
as  much  organic  matter  as  the  latter.  In  order  to  make  the 
figures  representing  the  total  number  of  organisms  bear  some 
close  relation  to  the  actual  character  of  the  water  as  shown 
by  the  physical  and  chemical  analyses,  it  was  suggested  that 
the  standard  unit  already  in  use  for  the  amorphous  matter 
might  be  applied  to  the  organisms  as  well.  This  "standard 
unit  method  "  was  adopted  at  the  Boston  Water  Works,  and 
has  been  used  extensively  elsewhere. 

The  unit  system  does  not  involve  much  extra  labor  in  the 
counting.  Many  organisms  are  so  constant  in  size  that  they 
may  be  counted  individually  and  then  reduced  to  standard 
units  by  multiplying  by  a  constant  factor.  Filamentous 
forms  of  constant  width  may  be  measured  in  length  and  then 
reduced  to  units.  Irregular  masses  and  variable  colonies  may 
be  estimated  directly  in  units.  In  practice  it  has  been  found 
desirable  to  modify  the  unit  somewhat  in  cases  where  organ 
isms  are  especially  thick  or  thin  in  order  that  the  results  may 
approximate  a  volumetric  determination  as  nearly  as  possible. 

It  is  not  always  that  the  unit  system  gives  better  results 
than  the  counting  system.  Sometimes  it  is  advisable  to  state 
the  results  both  in  number  of  individuals  and  in  standard  units. 


THE   MICROSCOPY   OF  DRINKING-WATER. 


MICROSCOPICAL    EXAMINATION. 

Sample  of  Croton  Water,  New  York. 

Date  of  Collection,  Aug.  25,  1897;  Date  of  Examination,  Aug.  25,  1897. 

Concentration,  500  cc.  to  10  cc.  Factor,  2. 


i 

2 

3 

4 

5 

6 

7 

8 

9 

10 

IS 
o 
h 

Number 
per  c.c. 

1-lS 

pk 

C/J 

DIATOMACE^E: 

i 

10 
2 

1 

I 

2 

I 
80 
40 

I 
I 

12 

5 
i 

i 

i 

3 

i 

i 
90 
30 

2 

2 

I 

I 

12 

8 

i 
7 

I 

4 

i 
i 

160 

5 

75 
10 

2 

IO 
10 

i 

8 
i 
ii 
4 

2 
2 

2 

2 

I30 
40 

I 

I 

9 

10 

i 

3<> 

240 

25 

25 

IO 
2 

I 

4 

; 

8 

2 
I 

5 

2 

I 
70 

IO 

I 
10 

4 

22 

6 

2 
I 

I 
2 

I 
I 

no 

5 

90 

2 

8 

i 

2 
19 

4 
4 

5 

4 

i 
i 

150 
75 

2 

I 

37 
7 

6 
6 

2 

IOO 

35 

2 

I 

2 

I 

ii 

6 

2 

4 

i 
5 
3 

no 

5° 

12 

16 
150 
51 
'9 
42 
13 

10 

4 

28 
15 
3 
30 
4 

1240 

10 

35 
470 
3° 

8 
4 

2 

18 

2 

5 

20 

6 

2 
I 

I 
I 

I 

24 
32 
300 

102 

38 
84 
26 
2O 

8 

10 

56 

% 
8 

20 

16 

8 

4 

36 

4 

IO 

i 
Present 

2 

9 
3 

150 

102 

s 

10 

40 

TOO 

56 

;i 

60 

so 

2480 

20 
50 
040 
60 

16 
8 
4 

18 
8 
60 
40 

12 

4 
16 

20 

4<> 

50 

10 

Cyclotella  

Synedra     

Tabellaria 

•CHLOROPHYCE^:: 

•CYANOPHYCE.*: 

Clathrocystis       

Microcystis  

FUNGI  AND  SCHIZOMYCETES: 

Mold  Hyphae 

Cladothrix  

PROTOZOA: 

Mallomonas  

Codonella 

H.OTIFBRA: 

Polyarthra  

CRUSTACEA: 
Cvcloos.  .  . 

OTHER  ORGANISMS: 

20 

25 

40 

25 

IS 

40 

20 

30 

35 

20 

270 

3 

6 

4647 

540 

6 

AMORPHOUS  MATTER  
MISCELLANEOUS  BODIES: 

METHODS   OF  MICROSCOPICAL   EXAMINATION. 


33 


SCHEDULES    OF    CLASSIFICATIONS    USED    AT    DIFFERENT 
TIMES    AND    IN  DIFFERENT    LABORATORIES. 


INDIVIDUAL  COUNTING  SYSTEM. 

STANDARD  UNIT  SYSTEM. 

Mass.  St.  Bd. 
of  Health, 
barker,  1887. 

Boston 
Water  Works. 
Whipple,  i88q* 

Mass.  St.  Bd. 
of  Health. 
Calkins,  i8qo. 

Conn.  St.  Bd. 
of  Health. 
i8qi. 

Brooklyn 
Water  Dept. 
W  hippie,  1897. 

Boston 
Water 
Works. 
Hollis,  1897. 

Diatomaceae 

Diatomaceae 

Diatomaceae 

Diatomacese 

Diatomaceae 

Diatomaceae 

Desmidieae 
Palmellaceae 
Zoosporeae 
Zygnemaceae 
Volvocinieae 

Desmidieas 
Chlorophyceae 

Algae 

Desmidieae 
Protococcoi- 
deae 
Confervaceae 

Chlorophyceae 

Chlorophyceae 

Cyanophyceae 

Cyanophyceae 

Cyanophyceae 

Cyanophyceae 

Cyanophyceae 

Cyanophyceae 

Schizomy- 
cetes 

Fungi 

Fungi 

Fungi 

Fungi  and 
Schizomycetes 

Fungi 

Protozoa 

Rhizopoda 
Infusoria 

Rhizopoda 
Infusoria 

Rhizopoda 
Infusoria 

Protozoa 

Rhizopoda 
Infusoria 

Rotifera 

Rotifera 

Vermes 

Rotifera 

Rotifera 

Rotifera 

Entomostraca 

Crustacea 

Crustacea 

Crustacea 

Crustacea 



Spongiaria 
Nematoda 
Annelida 

Miscellaneous 

Miscellaneous 
(including 
Zoogloea) 

Ova 

Spores 

Other 
Organisms 

Miscellane- 
ous 



Total 
Organisms 

Total 
Organisms 



Total 
Organisms 

Total 
Organisms 

Amorphous 
Matter 

Amorphous 
Matter 

Amorphous 
Matter 

Miscellaneous 
Bodies 

Records. — The  results  of  analysis  may  be  recorded  on  a 
blank  similar  to  the  one  shown  on  page  32.  The  ten  num- 
bered vertical  columns  correspond  to  ten  squares  counted. 
The  two  right-hand  columns  give  the  results  in  "  Number  per 
c.c."  and  in  "  Number  of  Standard  Units  per  c.c."  Either 


*  The  Standard  Unit  system  has  been  used  since  Jan.  i,  1893. 


34  THE   MICROSCOPY   OF  DRINKING-WATER. 

or  both  of  these  columns  may  be  used.  The  names  of  the 
common  organisms  are  given  in  the  left-hand  column,  and  are 
grouped  according  to  the  system  of  classification  described  in 
Part  II.  The  table  on  page  33  shows  the  schedules  of 
classification  used  by  different  observers.  It  may  be  found- 
useful  in  the  comparison  of  different  reports. 


II.  PLANKTON  NET  METHOD. 

The  plankton  net  *  consists  of  a  conical  net  of  silk  bolting- 
cloth  (No.  20)  suspended  from  an  iron  ring  two  feet  in 
diameter  (Fig.  7).  The  net  has  a  length  of  three  feet.  At 
the  lower  end  it  terminates  in  a  flat  metal  ring  to  which  is 
attached  the  filtering-bucket.  The  latter  consists  of  a  metal 
frame  covered  on  the  sides  with  bolting-cloth,  and  having  a 
slightly  conical  bottom.  In  the  middle  of  the  bottom  there 
is  an  outlet-tube  closed  with  a  removable  plug.  The  bucket 
is  about  2\  inches  in  diameter.  It  is  supported  on  three  legs 
when  detached  from  the  net.  The  filtering-net  of  bolting- 
cloth  is  protected  by  a  twine  net  which  helps  to  bear  the 
strain  when  the  net  is  drawn  through  the  water.  Cords 
extend  from  the  iron  ring  to  the  bucket  in  order  to  further 
relieve  the  filtering-net  from  strain.  Above  the  filtering-net 
there  is  a  truncated  canvas  cone  that  serves  as  a  guard,  pre- 
venting the  entrance  of  mud  when  near  the  bottom  and  pre- 
venting the  contents  of  the  net  from  spilling  over  the  edge. 
The  smaller  diameter  of  this  guard  is  about  16  inches.  It  is 
this  diameter  that  determines  the  volume  of  water  filtered 
when  the  net  is  drawn  through  the  water.  The  whole  net  is 

*  There  are  several  modifications  of  Hensen's  original  net.  The  form- 
used  by  Reighard  in  Lake  St.  Clair  and  here  described  may  be  considered 
as  typical. 


METHODS    OF  MICROSCOPICAL    EXAMINATION.  35 

suspended  by  three  cords  attached  to  radiating  iron  arms 
fastened  to  the  rope  by  which  the  apparatus  is  raised  and 
lowered. 


FIG.  7. — PLANKTON  NET.     (After  Reighard.) 

The  net  is  operated  as  follows:  It  is  lowered  to  the 
bottom  or  to  the  desired  depth  and  then' drawn  to  the  surface, 
the  velocity  of  its  ascent  being  noted.  On  the  way  down  it 
takes  in  no  water  except  what  is  filtered  through  the  gauze. 
On  the  way  up  it  filters  a  column  of  water  whose  cross-section 


3  THE   MICROSCOPY  OF  DRINKING-WATER. 

is  that  of  the  opening  of  the  guard  net  and  whose  height  is 
equal  to  the  distance  through  which  the  net  was  drawn. 
This  is  the  theoretical  amount  filtered.  In  practice  the  net 
does  not  strain  the  whole  column  of  water  through  which  it 
passes,  as  a  portion  of  the  water  is  forced  aside.  There- 
fore in  order  to  obtain  the  volume  of  plankton  in  the 
column  traversed  it  is  necessary  to  multiply  the  observed 
result  by  a  factor  or  coefficient.  This  net-coefficient  varies 
for  each  net  and  for  different  velocities  of  ascent  through  the 
water.  It  also  varies  with  the  amount  of  clogging.  With 
velocities  of  2  to  3  ft.  per  second  the  coefficient  is  about  2£. 
It  is  necessary  to  know  the  coefficient  for  each  net  at  different 
velocities  and  to  correct  the  results  of  each  haul  for  the  par- 
ticular velocity  used. 

When  the  net  reaches  the  surface  it  is  allowed  to  drain. 
A  stream  of  water  played  on  the  outside  of  the  net  detaches 
the  organisms  from  the  bolting-cloth  and  washes  them  down 
into  the  bucket.  The  bucket  is  then  detached  from  the  net 
and  its  collected  material  is  transferred  to  a  small  bottle  for 
transportation  to  the  laboratory. 

The  plankton  net  used  by  Birge  differs  from  the  one  just 
described  in  that  it  has  a  cover  instead  of  a  guard-net.  The 
cover  slides  in  a  rectangular  frame.  It  is  moved  by  delicately 
adjusted  weights  set  in  action  by  a  releasing  device  which  is 
operated  by  messengers  sent  down  the  rope.  The  cover  may 
be  opened  or  closed  at  any  depth  at  the  will  of  the  operator. 
This  enables  one  to  collect  material  from  the  lower  strata 
without  having  it  contaminated  with  that  above  it. 

The  amount  of  plankton  collected  may  be  determined 
by  four  methods:  (i)  by  estimation  of  the  volume;  (2)  by 
determination  of  the  weight;  (3)  by  chemical  analysis;  (4)  by 
enumeration  of  the  organisms. 


METHODS   OF  MICROSCOPICAL   EXAMINATION.  37 

The  volume  is  obtained  by  allowing  the  material  to  stand 
in  alcohol  in  a  graduated  cylinder  for  24  hours.  At  the  end 
of  that  time  the  plankton  will  have  settled  and  the  volume  in 
cubic  centimeters  may  be  read  from  the  scale.  This  gives 
the  total  volume  in  one  catch.  It  is  customary  to  express 
results  in  "number  of  cubic  centimeters  of  plankton  under 
one  square  meter  of  surface  "  or  in  "number  of  cubic  centi- 
meters of  plankton  in  one  cubic  meter  of  water." 

The  approximate  weight  may  be  determined  by  drying 
on  filter-paper  and  weighing.  The  results  are  usually  ex- 
pressed in  grams  of  plankton  under  one  square  meter  of 
surface  or  in  one  cubic  meter  of  water. 

The  chemical  analysis  of  the  plankton  usually  consists  of 
the  determination  of  the  percentage  of  organic  material,  ash, 
silica,  etc. 

The  enumeration  of  the  organisms  is  the  most  important 
part  of  the  laboratory  investigation.  The  material  is  evenly 
distributed  in  a  definite  amount  of  alcohol  by  shaking,  and  a 
portion  is  removed  to  a  small  trough  or  cell  and  placed  under 
the  microscope.  The  various  organisms  are  then  counted. 
Lines  drawn  on  the  bottom  of  the  cell  aid  the  observer  in 
covering  the  entire  area  of  the  cell.  As  in  the  case  of 
volume  and  weight,  the  results  are  generally  expressed  either 
in  "  number  of  organisms  under  one  square  meter  of  surface  " 
or  in  "  number  of  organisms  per  cubic  meter  of  water." 
Both  these  methods  are  objectionable  because  so  many  figures 
are  involved.  They  often  extend  to  the  millions  and  some- 
times to  the  billions.  It  is  preferable  to  express  the  smaller 
organisms,  such  as  the  algae  and  protozoa,  in  "number  per 
cubic  centimeter,"  and  the  larger  organisms,  such  as  the 
Crustacea,  rotifera,  etc.,  in  "  number  per  liter." 

It  is  evident  that  the  "  plankton  net  method  "  involves 


38  THE   MICROSCOPY   OF  DRINKING-WATER. 

many  sources  of  error.  Neither  the  amount  of  water  strained 
nor  the  completeness  of  the  filtration  can  be  definitely  ascer- 
tained. The  loss  of  the  smaller  organisms  by  leakage  through 
the  meshes  of  the  silk  is  very  great,  and  many  of  the  delicate 
organisms  are  crushed  upon  the  net.  The  methods  of 
estimating  the  volume  and  weight  of  the  plankton,  moreover, 
are  exceedingly  inaccurate.  The  met'hod  of  enumerating  the 
organisms  is  much  to  be  preferred.  Except  in  the  case  of 
comparatively  large  organisms,  such  as  the  Rotifera,  Crus- 
tacea, etc.,  the  results  of  the  net  method  cannot  be  depended 
upon  within  50  per  cent.  • 

III.  PLANKTON  PUMP. 

The  plankton  pump  is  designed  to  collect  the  plankton 
from  any  particular  depth  in  a  lake.  It  consists  of  a  sort 
of  force-pump  so  arranged  that  a  definite  and  measurable 
quantity  of  water  is  delivered  at  each  stroke;  an  adjustable 
hose  through  which  the  water  is  drawn  from  the  desired 
depth;  and  a  filtering-bucket  into  which  the  water  is  pumped. 
The  straining  is  effected  by  allowing  the  water  to  pass  through 
a  cylinder  of  fine  wire  gauze  at  the  lower  end  of  the  filtering- 
bucket.  The  efficiency  of  the  strainer  is  increased  by  cover- 
ing the  wire  gauze  with  fine  bolting-cloth. 

This  method  has  the  advantage  of  measuring  the  quantity 
of  water  strained  with  greater  accuracy  than  is  possible  in  the 
net  method,  but  the  error  from  imperfect  filtration  is  large. 

IV.  THE  PLANKTONOKRIT. 

The  planktonokrit  is  a  modification  of  the  centrifugal 
machine.  The  water  to  be  examined  is  placed  in  two  funnel- 


METHODS    OF  MICROSCOPICAL    EXAMINATION.  39 

shaped  receptacles  attached  to  an  upright  shaft,  with  the  necks 
of  the  funnels  pointed  outwards.  The  receptacles  have  a 
capacity  of  one  liter  each.  The  funnel  portion  is  made  of 
tinned  copper;  the  stem  is  a  glass  tube  that  has  a  bore  of  2^ 
to  5  mm.  The  glasses  are  held  in  place  by  a  cover,  such  as 
is  employed  in  mounting  a  water-gauge.  The  shaft  is  driven 
by  hand  or  belt  through  a  series  of  geared  wheels,  so  arranged 
that  50  revolutions  of  the  crank,  or  pulley-wheel,  produce 
8000  revolutions  of  the  upright  shaft.  By  this  rapid  revolu- 
tion of  the  sample  the  organisms  are  thrown  outwards  by 
centrifugal  force  and  collect  in  the  neck  of  the  funnel,  from 
which  they  may  be  removed  for  examination. 

There  are  certain  practical  objections  to  the  forms  of 
apparatus  now  constructed.  It  is  not  only  difficult  but 
dangerous  to  use  high  speeds  when  large  quantities  of  water 
are  operated  on.  Field  has  been  unable  to  use  a  speed 
greater  than  3000  revolutions  per  minute.  This  speed  main- 
tained for  four  minutes,  however,  was  sufficient  to  throw  out 
-all  the  organisms  except  the  Cyanophyceae.  By  reducing  the 
amount  of  the  samples  and  by  perfecting  the  mechanical 
parts  of  the  apparatus  it  seems  probable  that  excellent  results 
may  be  obtained  by  this  method. 

Comparison  of  the  methods  described  above  will  show 
that  the  Sedgwick-Rafter  method  and  the  planktonokrit  are 
designed  for  use  in  examining  samples  of  water  in  the  labora- 
tory, while  the  plankton  net  and  the  plankton  pump  are 
intended  for  field  work.  The  latter  are  most  serviceable  in 
concentrating  the  larger  microscopic  organisms  such  as  the 
Rotifera  and  Crustacea.  The  Sedgwick-Rafter  method  is  the 
most  practical  and  efficient  method  for  use  in  sanitary  water 
analysis.  It  should  not  be  relied  upon  completely,  but  should 


40  THE   MICROSCOPY   OF* DRINKING-WATER. 

be  supplemented  by  a  direct  microscopical  examination  of  the 
original  sample  of  water  or  by  the  use  of  the  planktonokrit. 

It  is  much  to  be  desired  that  all  results,  obtained  by 
whatever  method,  should  be  expressed  in  terms  of  the  same 
unit,  and  it  is  hoped  that  the  inconvenient  methods  of  express- 
ing results  in  "grams  or  cubic  centimeters  of  plankton  under 
one  square  meter  of  surface  or  in  one  cubic  meter  of  water  " 
will  be  abandoned  by  planktologists  and  the  more  exact 
system  of  counting  the  organisms  substituted. 


CHAPTER    IV. 

MICROSCOPIC  ORGANISMS   IN   WATER   FROM   DIFFERENT 

SOURCES. 

IN  studying  the  distribution  of  microscopic  organisms  it 
will  be  convenient  to  consider  the  following  classes  of  water- 
supply  separately: 

RAIN-WATER. 
GROUND-WATER. 
Springs. 
Wells. 

Infiltration-galleries. 
Infiltration-basins. 
SURFACE-WATER. 
Streams  and  Canals. 
Natural  Lakes  and  Ponds. 
Artificial  Reservoirs. 
FILTERED  WATER. 
Sand  Filtration. 
Mechanical  Filtration. 

Rain-water. — Rain-water  is  perhaps  the  purest  water 
found  in  nature,  yet  it  sometimes  contains  micro-organisms. 
For  the  most  part  they  are  so  minute  that  an  examination  by 
the  Sedgwick-Rafter  method  fails  to  reveal  them,  but  larger 
forms  are  sometimes  observed. 

The  study  of  the  organisms  found  in  rain-water  is  really 
the  study  of  the  organisms  found  in  the  air.  It  is  worthy  of 
more  attention  than  has  been  given  to  it.  The  presence  of 
organisms,  or  their  spores,  in  the  air  may  be  demonstrated  by 

41 


42  THE   M1CROSCOP  Y   OF  DRINKING-  WA  TER. 

sterilizing  some  water  rich  in  nitrogenous  matter  and  expos- 
ing it  to  the  air  in  the  light.  After  a  week  or  two  it  will 
contain  numerous  forms  of  microscopic  organisms  which 
must  have  settled  into  the  liquid  from  the  air  or  developed 
from  spores  floating  in  the  air. 

Rain-water  collected  in  a  sterilized  jar  and  allowed  to 
stand  protected  from  the  air  often  develops  a  considerable 
growth  of  algae  (usually  some  Protococcus  form),  showing  that 
the  rain  has  not  only  taken  up  the  organisms  or  their  spores, 
Ijut  has  absorbed  sufficient  food  material  for  their  growth. 
Samples  of  rain-water  sometimes  contain  a  surprisingly  large 
.amount  of  nitrogenous  matter,  especially  if  collected  in  the 
vicinity  of  a  large  city  and  at  the  beginning  of  a  storm. 

It  has  been  noticed' frequently  that  vigorous  growths  of 
algae  have  appeared  in  ponds  or  reservoirs  immediately  after  a 
rain-storm,  the  growth  occurring  suddenly  and  simultaneously 
throughout  the  whole  body  of  water.  It  is  possible  that 
these  sudden  growths  may  be  caused  by  the  dried  spores  of 
the  algae  being  lifted  from  the  shores  of  the  ponds  and  scat- 
tered through  the  air  by  the  wind,  and  then  washed  into  the 
water  by  the  rain.  This  supposition  is  in  harmony  with  the 
theory  that  in  the  case  of  certain  algae  sporadic  development 
occurs  only  after  the  desiccation  of  the  spores. 

Ground-water. — Ground-water  is  water  that  has  filtered 
or  percolated  through  the  ground.  It  comes  to  the  surface 
as  springs  or  is  collected  in  wells  or  infiltration-galleries. 

Ground-water  collected  directly  from  the  soil  before  it  has 
had  an  opportunity  to  stand   in  pipes  or  be  exposed  to  the 
light  is  almost  invariably  free  from   microscopic    organisms 
Its  passage  through  the  soil  filters  them  out.      It  usually  con- 
tains an  abundant  supply  of  plant  food,  extracted  from   the 


MICROSCOPIC  ORGANISMS   IN    WA  TER.  43 

organic  and  mineral  matter  of  the  soil  and  modified  by  bac- 
terial action,  and  when  the  water  reaches  the  light  this  food 
material  is  seized  by  the  micro-organisms.  One  will  recall 
the  luxuriant  aquatic  vegetation  at  the  mouth  of  some  spring 
or  in  some  watering-trough  supplied  with  spring-water. 
Organisms  are  occasionally  met  with  in  ground-water  supplies, 
but,  with  the  exception  of  the  Schizomycetes,  the  number  of 
organisms  depends  upon  the  exposure  of  the  water  to  the 
light  and  air;  that  is,  it  is  only  as  a  ground-water  becomes  a 
surface-water  that  the  microscopic  organisms  develop. 

The  following  table,  compiled  from  the  examinations  of 
the  Massachusetts  State  Board  of  Health,  gives  an  idea  of  the 
organisms  met  with  in  ground-water  supplies.  Except  in  the 
case  of  springs,  the  figures  represent  the  average  of  monthly 
observations  extending  over  one  or  more  years. 

Spring-waters  usually  contain  no  microscopic  organisms. 
.Several  exceptions  are  noted  in  the  table, — one  at  Westport, 
where  45  5  Himantidium  were  present,  and  one  at  Millis,  where 
the  water  contained  180  Chlamydomonas  per  cc.  That  these 
were  accidental  is  shown  by  the  fact  that  in  1893  five  exami- 
nations of  the  Aqua  Rex  Spring  showed  an  entire  absence  of 
organisms. 

Well-waters  also  are  ordinarily  free  from  organisms,  but 
in  some  cases  Crenothrix  grows  abundantly  in  the  tubes  of 
driven  wells.  This  is  particularly  true  if  the  water  is  rich  in 
iron  and  organic  matter  and  deficient  in  oxygen.  Wells 
driven  in  swamps  are  often  thus  affected.  The  tubular  wells 
at  Provincetown  are  an  example,  Crenothrix  is  sometimes 
found  there  as  abundant  as  20000  per  c.c.  The  water  con- 
tains more  than  0.125  parts  of  albuminoid  ammonia  per  mil- 
lion, and  the  iron  varies  from  i.oo  to  5.00  parts  per  million. 
Many  similar  cases  might  be  cited.  Leptothrix  and  Spiro- 
>chaete  forms  are  also  observed  in  well-waters  rich  in  iron. 


44 


THE  MICROSCOP  Y   OF  DRINKING-  WA  TER. 


MICROSCOPIC  ORGANISMS  IN  GROUND-WATERS. 
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MICROSCOPIC  ORGANISMS  IN    WAITER.  45 

Crenothrix  grows  in  tufts  or  in  felt-like  layers  on  the  inner 
walls  of  the  tubes.  By  the  deposition  of  iron  oxide  in  its 
gelatinous  sheath  it  clogs  up  the  tubes  and  strainers  with  iron- 
rust. 

Infiltration-galleries,  or  filter-galleries,  are  practically 
elongated  wells  located  near  some  stream  or  pond.  They  are 
similar  to  wells  in  regard  to  the  presence  of  micro-organisms. 
Few  organisms  other  than  Crenothrix  are  found. 

Infiltration-basins,  or  filter-basins,  are  infiltration-galleries 
open  to  the  light.  The  water  in  them  is  sometimes  affected 
with  algae-growths.  The  infiltration-basin  at  Taunton,  Mass., 
for  example,  has  given  trouble  from  this  cause.  In  October 
1894  there  were  more  than  1000  Asterionella  per  c.c.  present, 
and  they  were  followed  by  a  vigorous  growth  of  Dinobryon. 
Infiltration-basins  are  practically  open  reservoirs  for  the  stor- 
age of  ground-water — a  subject  to  be  treated  in  another 
chapter. 

Surface-water. — The  term  "  surface-water"  includes  all 
•collections  of  water  upon  the  surface  of  the  earth,  i.e.,  lakes, 
ponds,  rivers,  pools,  ditches,  etc. 

The  following  table  shows  that  surface-waters  contain 
many  more  microscopic  organisms  than  ground-waters,  and 
that  standing  water  contains  more  organisms  than  running 
water. 

Samples  from  rivers,  unless  collected  near  the  shore, 
seldom  contain  many  organisms,  and  water-supplies  drawn 
from  rivers  and  subjected  to  limited  storage  are  not  often 
troubled  with  animal  or  vegetable  growths.  This  may  be 
true  even  where  the  banks  of  the  stream  are  covered  with 
aquatic  vegetation.  The  organisms  found  in  streams  are 
largely  sedentary  forms.  Their  food-supply  is  brought  to  them 
by  the  water  continually  passing.  In  quiet  waters  there  are 
found  free-swimming  forms  that  must  go  in  search  of  their 


46 


MICROSCOPY   OF  DRINKING-  WA  TEX. 


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MICROSCOPIC  ORGANISMS   IN    WATER.  47 

food.  It  is  difficult  to  draw  a  sharp  line  between  these  two 
classes  of  organisms.  Some  are  free-swimming  at  will  or 
during  a  part  of  their  life-history,  and  some  free-swimming 
organisms  are  always  found  associated  with  sedentary  forms. 
On  most  rivers  there  are  some  quiet  pools  where  free-swim- 
ming forms  may  develop.  In  a  sample  of  river-water,  then, 
one  is  likely  to  find  sedentary  forms  which  have  become 
detached,  organisms  which  have  developed  in  the  quiet  places 
or  in  tributary  ponds,  and  spores  or  intermediate  forms  in  the 
life- history  of  sedentary  organisms.  In  streams  draining 
large  ponds  or  lakes  the  water  naturally  has  the  character  of 
the  pond-  or  lake-water,  and  organisms  may  be  abundant. 

The  number  of  microscopic  organisms  found  in  rivers  is 
subject  to  great  fluctuations.  If  the  water  is  rich  in  food- 
material,  littoral  growths  often  develop  with  rapidity,  while  a 
heavy  rain  that  increases  the  current  of  the  water  and  the 
amount  of  scouring  material  that  it  carries  may  suddenly  wash 
away  the  entire  growth.  With  such  conditions  the  number  of 
organisms  collected  in  a  sample  may  be  above  the  normal. 
At  other  times  a  rain  may  diminish  the  number  of  organisms 
in  a  sample  by  dilution.  But  the  fluctuations  are  due  chiefly 
to  changes  that  take  place  in  the  growths  in  tributary  ponds 
or  swamps,  and  to  the  fact  that  rains  may  cause  these  ponds 
to  overflow. 

The  table  shows  that  the  Diatomaceae  are  the  organisms 
found  most  constantly  in  rivers.  Navicula,  Cocconema, 
Gomphonema  and  other  attached  forms  are  common,  but 
their  numbers  are  small  compared  to  those  found  in  standing 
water.  Some  of  the  Chlorophyceae,  particularly  Conferva, 
Spirogyra,  Draparnaldia  and  other  filamentous  forms,  are 
often  observed.  The  Cyanophyceae,  except  the  Oscillarieae, 
seldom  occur.  Stony  Brook,  in  the  table,  represents  a  stream 


48  THE  MICROSCOP  Y  OF  DRINKING-  WA  TER. 

affected  by  tributary  ponds  where  Cyanophyceae  abound. 
Crenothrix  is  quite  often  found  in  river-water.  Anthophysa 
is  often  mistaken  for  it,  and  this  may  account  in  part  for  the 
high  figures  in  the  table.  Animal  forms  are  not  common  in 
rivers  unless  the  water  is  polluted.  Rotifera  and  Crustacea 
are  seldom  seen,  but  Protozoa  are  sometimes  observed. 

In  the  slow-running  water  of  canals  and  ditches  organ- 
isms sometimes  develop  in  large  numbers,  but  the  conditions 
are  not  often  such  as  to  cause  trouble  in  public  water-sup- 
plies. The  following  instance,  however,  is  worth  noting: 

On  Sunday,  July  12,  1896,  it  was  observed  by  some  of 
the  residents  living  in  the  western  part  of  the  city  of  Lynn, 
Mass.,  that  the  water  drawn  from  the  service-taps  had  a 
green  color.  A  glass  of  it  showed  a  heavy  green  sediment 
when  allowed  to  stand  even  for  a  few  minutes.  On  the 
following  day  it  became  worse,  and  when  the  water  was 
used  for  washing  in  the  laundry  it  was  found  to  leave 
green  stains  on  the  clothes.  These  acted  like  grass- 
stains.  Investigation  showed  that  the  stains  were  caused  by 
Raphidomonas,  and  that  these  organisms  were  abundant  in 
the  city  water.  Examination  of  the  four  storage-reservoirs 
showed  that  they  were  not  present  there  in  sufficient  numbers 
to  account  for  the  trouble.  The  water  from  one  of  the 
supply-reservoirs,  Walden  Pond,  reaches  the  pumping-station 
by  means  of  an  open  canal,  tunnel,  and  pipe-line.  It  was  in 
this  open  canal  that  the  Raphidomonas  were  found.  The 
sides  of  the  canal  were  thickly  covered  with  filamentous  algae, 
chiefly  Cladophora.  The  water  in  the  canal  had  a  dark  green 
color.  When  a  bottle  of  it  was  held  to  the  light  it  was 
almost  opaque  and  was  seen  to  be  densely  crowded  with 
moving  green  organisms.  As  many  as  2000  per  c.c.  were 
present.  Evidently  the  organisms  had  developed  among  the 


MICROSCOPIC   ORGANISMS  IN    WA  TER.  49 

algae  in  the  canal  and  had  gradually  scattered  themselves  out 
into  the  water  from  Walden  Pond  as  it  passed  through  the 
canal  on  its  way  to  the  city.  The  trouble  was  remedied  by 
emptying  the  canal  through  the  wasteways  and  cleaning  the 
slopes  to  prevent  later  development. 

This  is  the  only  case  on  record  where  Raphidomonas  has 
caused  trouble,  though  the  organism  is  often  found  in  sur- 
face-water supplies. 

Quiescent  Waters.  —  All  quiescent  surface-waters  are 
liable  to  contain  microscopic  organisms  in  considerable  num- 
bers. The  water  that  is  entirely  free  from  them  is  very  rare. 
It  is  scarcely  possible  to  collect  a  sample  of  stagnant  water  at 
any  season  of  the  year  without  obtaining  one  or  more  forms 
of  microscopic  life.  The  extent  and  character  of  the  growths 
vary  greatly  in  different  ponds  and  at  different  seasons. 

As  it  is  in  ponds  and  lakes  and  reservoirs  that  the  micro- 
scopic organisms  cause  the  most  trouble,  it  is  these  bodies  of 
water  that  chiefly  interest  us.  Before  considering  the  organ- 
isms in  this  class  of  water-supplies  it  is  important  to  know 
something  about  the  physical  conditions  of  water  in  ponds 
and  lakes.  These  are  discussed  in  the  following  chapter.  In 
passing,  one  should  observe  from  the  table  that  all  classes  of 
organisms,  except  perhaps  the  Schizophyceae,  are  much  more 
abundant  in  natural  ponds  and  in  reservoirs  than  in  rivers. 

Filtered  Water. — Water  which  has  been  filtered  either  by  the 
method  of  slow  sand  filtration  or  by  mechanical  filtration  seldom 
contains  many  microscopic  organisms.  In  the  case  of  slew  sand 
filtration  their  presence  in  the  filtered  water  generally  indicates 
that  the  filtration  is  imperfect.  In  the  case  of  mechanical  filtra- 
tion, however,  microscopic  organisms  sometimes  do  appear  in 
the  effluent,  although  nearly  always  in  small  numbers.  This 
is  apparently  due  in  part  to  the  use  of  coarser  sand  and  a  higher 


50  THE   MICROSCOPY   OP    DRINKING-WATER. 

rate  of  filtration  and  in  part  to  the  fact  that  the  organisms  be- 
come attached  to  the  sand  grains  near  the  surface  and  that  some 
of  these  sand  grains  are  carried  to  the  bottom  of  the  tank  during 
the  process  of  washing,  where  the  organisms  become  dislodged 
from  them.  The  presence  of  a  few  microscopic  organisms  in  the 
effluent  of  a  mechanical  filter,  therefore,  does  not  necessarily 
indicate  imperfect  filtration. 

Occasionally  growths  of  Crenothrix  and  allied  species  occur 
in  the  under-drains  of  sand  filters.  They  usually  appear  where 
the  conditions  are  such  that  the  water  is  deprived  of  part  of  its 
oxygen,  or  where,  through  leakage,  ground-water  containing 
iron  and  carbonic  acid  in  solution  becomes  mixed  with  the  filtered 
water. 

Growths  of  microscopic  organisms  often  occur  in  filtered  water 
when  exposed  in  open  reservoirs  to  the  sunlight,  as  described  in 
Chapter  XI.  Under  these  conditions  the  water  is  practically  a 
ground-water. 


CHAPTER    V. 
LIMNOLOGY. 

LIMNOLOGY  is  that  branch  of  science  that  treats  of  lakes 
and  ponds, — their  geology,  their  geography,  their  physics, 
their  chemistry,  their  biology,  and  the  relations  of  these  to 
each  other.  This  subject  has  taken  shape  only  within  the 
past  fifteen  years,  but  already  many  valuable  publications 
have  appeared. 

In  this  chapter  it  is  possible  to  consider  only  such  limno- 
logical  studies  as  are  closely  related  to  the  microscopic  organ- 
isms. The  most  important  of  these  are:  the  temperature 
of  the  water,  the  amount  of  light  received  and  transmitted  by 
the  water,  and  the  food  material  of  the  organisms  found  in 
the  water.  The  location  of  lakes,  their  shape,  size,  and 
depth,  the  source  of  their  supply,  the  character  of  the  water^ 
shed,  the  meteorology  of  the  region, — all  have  their  effect 
upon  the  organisms  living  in  the  water,  but  they  can  be  con- 
sidered only  incidentally. 

Physical  Properties  of  Water. — The  density  of  water 
varies  with  its  pressure,  with  its  temperature,  and  with  the 
substances  dissolved  in  it. 

Grassi  gives  the  coefficient  of  compressibility  of  pure 
water  as  .0000503  per  atmosphere  at  o°  C.,  and  .0000456  at 
25°  C.  Therefore  if  the  density  at  the  surface  of  a  lake  is 
unity,  at  a  depth  of  339  ft.  (10  atmospheres)  it  will  be  1.0005  ^ 


THE   MICROSCOP  Y   OF  DRINKING-  IV A  TER. 


at  678  ft.  (20  atmospheres),  i.ooi ;   and  at  1017  ft.  (30  atmos- 
pheres),  1.0015. 

Water  attains  its  maximum  density  at  about  4°  C.  or 
39.2°  F.  Assuming  its  density  at  4°  C.  to  be  unity,  its 
density  at  other  temperatures  is  given  in  the  following  table. 

DENSITY    OF   WATER   AT    DIFFERENT    TEMPERATURES. 


Temperature. 

Temperature. 

Density. 

Density. 

Centigrade. 

Fahrenheit. 

Centigrade. 

Fahrenheit. 

0° 

32.00 

.99987 

IS.3° 

65.0° 

.99859 

1.6 

1        35-0 

.99996 

21.  1 

7O.O 

.  99802 

4-0. 

39-2 

I  .  OOOOO 

23-8 

75-0 

•99739 

4-4 

40.0 

.99999 

26.6 

80.0 

.  99669 

7.2 

45-0 

.  99992 

29.4 

85.0 

.99591 

10.  0 

50.0 

•99975 

32.2 

90.0 

.99510 

12.7 

55-0 

.99946 

35-0 

95-0 

.99418 

15-5 

60.0 

.99907 

37-7 

IOO.O 

.99318 

Water  freezes  at  o°  C.,  or  32.0°  F.     Ice  is  lighter  than  water.     It  readily 
floats  in  water  at  o°  C, 

Water  has  a  very  high  specific  heat.  It  is  a  poor  thermal 
conductor.  Prof.  W.  H.  Weber*  gives  its  coefficient  of 
conductivity  as  0.0745. 

Water  is  extremely  mobile.  This  property  renders  it 
subject  to  displacement  by  mechanical  agencies,  such  as  wind 
and  currents  (mechanical  convection),  and  permits  it  to 
become  stratified  according  to  the  density  of  its  particles. 
The  mobility  of  water  varies  somewhat  with  its  temperature, 
Ibeing  greater  as  the  temperature  is  higher. 

When  water  is  stratified  with  the  warmer  layers  above  the 
•colder,  the  stratification  is  said  to  be  ''direct."  This  occurs 
when  the  temperatures  are  above  that  of  maximum  density. 
When  water  is  stratified  with  the  colder  layers  above  the 


warmer   the   stratification    is    said   to   be   "  inverse. 


This 


*  Vierteljahreschrift  der  Zurich  Nat.  Ges.,  xxiv.  252,  1879. 


LIMNOLOGY.  53 

occurs  when  the  temperatures  are  below  that  of  maximum 
density.  With  the  temperatures  above  39.2°  it  sometimes 
happens  in  a  deep  lake  that  a  colder  layer  of  water  is  found 
above  a  warmer  layer.  This  is  a  paradox  theoretically  possi- 
ble, because  the  density  of  the  water  at  any  point  in  a  lake 
depends  upon  its  depth  as  well  as  its  temperature.  Thus, 
water  at  45°  F.  has  a  density  of  .99992.  If  this  water  were 
at  a  depth  of  1017  ft.,  where  the  pressure  is  30  atmospheres 
its  density  would  be  .99992  -{-  .0015  =  1.00142,  i.e.,  more 
than  that  of  water  at  39.2°  F.  at  the  surface.  In  nature, 
however,  such  a  condition  of  temperatures  seldom  exists  for 
a  long  period,  and  practically  represents  a  state  of  unstable 
equilibrium.  A  thermal  paradox  may  be  caused  also  by 
differences  in  the  density  of  different  strata  due  to  substances 
in  solution. 

Water  has  a  slight  power  of  diathermancy,  i.e.,  it  permits 
the  penetration  of  radiant  heat  to  a  slight  degree.  Forel 
experimented  on  the  diathermancy  of  water  by  comparing 
the  readings  of  thermometers  with  blackened  and  with  ordi- 
nary bulbs  at  a  depth  of  I  metre.  He  obtained  the  following 
results: 

Time  Temperature      Excess  of  Temperature 

Date.  of  of  Water.      of  Black  Bulb  Thermom- 

Exposure.  (Fahrenheit.)         eter,  in  Fahr.  Deg. 

Mar.  27,  1871  10  hours  44-4°  10.8° 

July  25,  1873  17      "  72.0  14.0 

"       26,  1873  15       "  74-3  15-3 

Aug.    i,  1873  12      "  75.2  7.6 

THE   TEMPERATURE    OF    LAKES   AND    PONDS. 

Methods  of  Observation. — The  observation  of  the  tem- 
perature of  the  water  at  the  surface  of  a  lake  is  a  compara- 
tively easy  matter,  but  it  requires  an  accurate  thermometer 
a  careful  observer.  Where  the  water  is  smooth  the 


54  THE   MICROSCOPY   OF  D  RrttKlNC-WATER. 

thermometer-bulb  may  be  immersed  just  beneath  the  surface 
in  an  inclined  position  and  the  reading  taken  before  removing 
it  from  the  water.  In  taking  the  reading  one  must  be  careful 
to  avoid  parallax  by  holding  the  thermometer  exactly  at  right 
angles  to  the  line  of  sight.  When  the  water  is  too  rough  for 
reading  directly  some  of  the  surface-water  may  be  dipped  up 
and  the  temperature  of  that  ascertained.  Thermometers  with 
bulb  immersed  in  a  cup  are  prepared  for  this  purpose.  Direct 
observations  are  much  to  be  preferred. 

The  observation  of  the  temperature  of  the  water  at 
depths  below  the  surface  is  more  difficult. 

The  simplest  method  of  obtaining  results  that  are  in  any 
way  accurate  is  to  enclose  a  weighted  thermometer  in  a 
stoppered  empty  bottle  and  to  lower  this  to  the  proper  depth 
and  fill  it  by  drawing  out  the  stopper.  After  allowing  a 
sufficient  time  for  the  apparatus  and  thermometer  to  acquire 
the  exact  temperature  of  the  water  the  bottle  is  drawn  to  the 
surface  and  the  reading  taken  before  the  thermometer  is 
removed  from  the  bottle.  If  the  bottle  is  of  sufficient  size, 
if  it  is  allowed  to  remain  down  long  enough,  if  it  is  drawn 
rapidly  to  the  surface  and  the  reading  taken  at  once,  the 
error  ought  not  to  exceed  one  degree  Fahrenheit.  This 
method  is  impracticable  for  lakes  much  deeper  than  50  ft.,  and 
beyond  that  depth  some  form  of  deep-sea  thermometer  is 
necessary.  Several  forms  of  maximum  and  minimum  ther- 
mometers and  of  self-setting  thermometers  have  been  devised. 
The  Negretti  and  Zambra  thermometers  have  been  used 
extensively  for  obtaining  the  temperature  of  very  deep  water. 
Several  forms  of  electrical  thermometers  have  been  suggested, 
but  the.  thermophone*  is  the  only  one  that  has  proved  of 
practical  value. 

*  Invented  and  patented  by  H.  E.  Warren  and  G.  C.  Whipple. 


LIMNOLOGY, 


55 


The  thermophone  (see  Fig.  8)  is  an  electrical  thermom- 
eter of  the  resistance  type.  It  is  based  upon  the  principle 
that  the  resistance  of  an  electrical  conductor  changes  with  its 
temperature  and  that  the  rate  of  change  is  different  for  differ- 


FIG.  8. — THERMOPHONE,  PORTABLE  FORM.    (After  Warren  and  Whipple.) 

ent  metals.  Two  resistance-coils  of  metals  that  have  different 
electrical  temperature-coefficients,  as  copper  and  German 
silver,  are  put  into  adjacent  arms  of  a  Wheatstone  bridge  and 
located  at  the  place  where  the  temperature  is  desired,  the  two 
coils  being  joined  together  at  one  end,  The  other  extremi- 
ties of  the  coils  are  connected  by  leading  wires  to  the 


56  THE  MICROSCOPY  OF  DRINKING-WATER. 

terminals  of  a  slide-wire  which  forms  a  part  of  the  indicator. 
A  third  leading  wire  extends  from  the  junction  of  the  two 
coils  to  a  movable  contact  on  the  slide-wire,  having  in  its  cir- 
cuit a  telephone  and  a  current-interrupter, — the  latter  oper- 
ated by  an  independent  battery  connection.  The  telephone 
and  interrupter  serve  as  a  galvanometer  to  detect  the  presence 
of  a  current.  The  slide-wire  is  wound  around  the  periphery 
of  a  mahogany  disc,  above  which  there  is  another  disc  carry- 
ing a  dial  graduated  in  degrees  of  temperature.  The  movable 
contact  which  bears  on  the  slide-wire  is  attached  to  a  radial 
arm  placed  directly  under  the  dial-hand,  the  two  being 
moved  together  by  turning  an  ebonite  knob  in  the  centre  of 
the  dial.  This  indicator  is  enclosed  in  a  brass  case  in  a  box 
that  also  contains  the  batteries.  The  sensitive  coils  are 
enclosed  in  a  brass  tube  of  small  diameter  which  is  filled  with 
oil,  hermetically  sealed,  and  coiled  into  a  helix.  Connections 
with  the  leading  wires  are  made  in  an  enlargement  at  one  end. 
The  leading  wires  are  three  in  number  and  are  made  to  form 
a  triple  cable.  The  temperature  of  the  leading  wires  does  not 
affect  the  reading  of  the  instrument  because  two  of  them  are 
of  low  resistance  and  are  on  opposite  sides  of  the  Wheatstone 
bridge.  They  neutralize  each  other.  The  third  leading  wire 
is  connected  with  the  galvanometer  and  does  not  come  into 
the  question.  The  readings  of  the  instrument  are  independ- 
ent of  pressure. 

The  operation  of  taking  a  reading  is  as  follows:  The  coil 
is  lowered  to  the  depth  where  the  temperature  is  desired, 
the  three  leading  wires  are  connected  to  the  proper  binding- 
posts  of  the  indicator-box,  the  current  from  the  battery 
is  turned  on,  the  telephone  is  held  to  the  ear,  and  the  index 
moved  back  and  forth  over  the  dial.  A  buzzing  sound 
will  be  heard  in  the  telephone,  increasing  or  diminishing  as 


LIMNOLOGY. 


the  index  is  made  to  approach  or  recede  from  a  certain  sec- 
tion of  the  dial.  A  point  may  be  found  at  which  there  is 
perfect  silence  in  the  telephone,  and  at  this  point  the  hand 
indicates  the  temperature  of  the  distant  coil.  With  thermo- 
phones  adjusted  for  atmospheric  range,  i.e.,  from  —  15° 
to  115°  F.,  readings  correct  to  o. i°  F.  may  be  made.  With 
a  smaller  range  greater  precision  may  be  obtained. 

Because  of  its  accuracy,  because  of  the  ease  with  which 
the  coil  may  be  placed  at  any  depth  from  the  surface  to  the 
bottom  of  a  lake,  because  of  its  extreme  sensitiveness  and 
rapidity  of  setting  (one  minute  is  sufficient),  and  because  of 
its  portability,  the  thermophone  is  better  adapted  than  any 
other  instrument  for  taking  series  of  temperature  observations 
in  lakes  at  various  depths.  It  has  been  used  for  that  purpose 
at  depths  as  great  as  400  ft.,  and  it  was  used  by  Prof.  A.  E. 
Burton  in  Greenland  at  much  greater  depths  for  obtaining 
temperatures  in  the  crevasses  of  glaciers. 

Results  of  Observations. — The  temperature  changes 
that  take  place  in  a  body  of  water  may  be  illustrated  by  a 


70' 
60° 

50= 
40° 

OAC 

/ 

<- 

N 

70' 
60° 
50° 
40° 
30" 

/ 

/ 

\ 

,1 

f 

\ 

/ 

B 

)TTC 

)M 

X 

(/• 

1 

7 

Tl 
L* 

:MPERATU 

KE  COCHr 

}E 
UA 

OF 
FE 

V 

JAN. 

FEB. 

MAR, 

APR. 

MAY 

JUNEJULYJAUG. 

SEP. 

OCT. 

NOV. 

DEC. 

FIG.  9. 

diagram  that  shows  the  temperatures   at   the  surface   and 
bottom  of  Lake  Cochituate.     The  curves  of  Fig.  9  are  based 


58  THE   MICROSCOPY   OF  DRINKING-WATER. 

on   a   seven-years   series   of   weekly    observations,    but   some 
irregularities  have  been  omitted  for  the  sake  of  simplicity. 

If  one  traces  the  line  of  surface  temperatures,  he  will 
observe  that  during  the  winter  the  water  immediately  under 
the  ice  stands  substantially  at  32°  F.,  though  the  ice  itself 
often  becomes  much  lower  than  32°  at  its  upper  surface.  As 
soon  as  the  ice  breaks  up  in  the  spring  the  temperature  of  the 
water  begins  to  rise.  This  increase  continues  with  some 
-fluctuations  until  about  the  first  of  August.  Cooling  then 
begins  and  continues  regularly  through  the  autumn  until  the 
lake  freezes  in  December.  If  this  curve  of  surface  tempera- 
ture were  compared  with  the  mean  temperature  of  the  atmos- 
phere for  the  same  period  a  striking  agreement  would  be 
noticed,  and  it  would  be  seen  that  the  water  temperature 
is  the  higher  of  the  two.  When  the  surface  is  frozen 
there  is  no  comparison  between  the  air  and  water  tempera- 
tures. During  the  spring  and  early  summer,  when  the  water 
is  warming,  the  water  is  but  slightly  warmer  than  the  air,* 
but  during  the  late  summer  and  autumn  it  is  about  5° 
warmer.  The  surface  temperature  of  the  water  fluctuates 
with  the  air  temperature  during  the  course  of  the  day  as  well 
as  on  different  days.  The  maximum  is  usually  obtained 
between  2  and  4  P.M.  and  the  minimum  between  5  and  7  A.M. 
The  daily  range  is  seldom  greater  than  5°,  though  it  may  be 
much  more.  At  the  latitude  of  Boston  the  maximum  sur- 
face temperature  of  the  water  of  lakes  during  the  summer  is 
seldom  above  80°. f 


*  It  must  be  understood  that  it  is  the  mean  temperature  of  the  air 
during  24  hours  that  is  referred  to,  and  not  the  maximum  temperature 
during  the  daytime. 

f  A  surface  temperature  of  92°  was  observed  by  the  author  at  Chestnut 
Hill  Reservoir  on  Aug.  12,  1896,  at  3  P.M.,  after  a  week  of  excessively  hot 
weather,  during  which  the  maximum  daily  temperature  remained  above 


LIMNOLOG  Y.  59 

In  small  shallow  ponds  the  surface  temperature  follows 
the  atmospheric  temperature  much  more  closely  than  in  large 
deep  lakes  where  the  water  circulates  to  considerable  depths. 
In  the  latter  the  surface  temperature  is  often  below  that  of 
the  mean  atmospheric  temperature  during  the  early  part  of 
the  summer,  and  occasionally  during  the  entire  summer. 

Lake  Cochituate  is  60  ft.  deep.  The  temperature  at  the 
bottom  during  the  winter,  when  the  surface  is  frozen,  is  not 
far  from  that  of  maximum  density  (39.2°  F.).  The  heaviest 
water  is  at  the  bottom;  the  lightest  is  at  the  top;  and  the 
intermediate  layers  are  arranged  in  the  order  of  their  density. 
With  these  conditions  the  water  is  in  comparatively  stable 
equilibrium.  It  is  inversely  stratified.  It  is  the  period  of 
"  winter  stagnation." 

As  soon  as  the  ice  has  broken  up  in  the  spring  the  sur- 
face-water begins  to  grow  warmer.  Until  it  reaches  the 
temperature  of  maximum  density  it  grows  more  dense  as  it 
grows  warmer,  and  as  it  becomes  denser  it  tends  to  sink. 
Thus  until  the  water  throughout  the  vertical  has  acquired  the 
temperature  of  maximum  density  there  are  conditions  of 
unstable  equilibrium  caused  by  diurnal  fluctuations  of  tem- 
perature that  result  in  the  thorough  mixing  of  all  the  water 
in  the  lake  These  conditions,  together  with  the  mechanical 
effect:  of  the  wind,  usually  cause  a  slight  temporary  lowering 
of  the  bottom  temperature  at  this  season.  Finally  the  tem- 

90°,  while  the  humiaity  varied  from  62$  to  95$.  At  the  time  of  the  obser- 
vation the  air  temperature  was  95°  arid  the  humidity  70$.  The  temperatures 
of  the  water  below  the  surface  were  as  follows  : 

Surface 92.0°  10  ft 76.2° 

i  ft QI.5  15  " 74-0 

2" 89.2  2O" 65.7 

3  "..... 85.6  25  " 54-5 

4  " 80.2  27  " 53.1 

5  " 79-0 


60  THE   MICROSCOPY   OF  DRINKING-WATER. 

perature  throughout  the  vertical  becomes  practically  uniform,, 
and  vertical  currents  are  easily  produced  by  slight  changes  in 
the  temperature  of  the  water  at  the  surface  and  by  the 
mechanical  effect  of  the  wind. 

This  is  the  period  of  "  spring  circulation  "  or  the  "  spring 
overturning."  It  lasts  several  weeks,  but  varies  in  duration 
in  different  years.  As  the  season  advances  the  surface-water 
becomes  warmer  than  that  at  the  bottom,  and  finally  the 
difference  becomes  so  great  that  the  diurnal  fluctuation  of 
surface  temperature  and  the  effect  of  the  wind  are  no  longer 
able  to  keep  up  the  circulation.  Consequently  the  bottom 
temperature  ceases  to  rise,  the  water  becomes  "  directly 
stratified,"  and  the  lake  enters  upon  the  period  of  "  summer 
stagnation."  During  this  period,  which  extends  from  April 
to  November,  the  bottom  temperature  remains  almost  con- 
stant, and  the  water  below  a  depth  of  about  25  ft.  remains 
stagnant.  In  the  autumn  the  surface  cools  and  the  water 
becomes  stirred  up  to  greater  and  greater  depths,  until  finally 
the  "  great  overturning  "  takes  place  and  all  the  water  is  in 
circulation.  At  this  time  there  is  a  slight  increase  in  the 
bottom  temperature  that  corresponds  to  the  temporary 
lowering  of  the  temperature  in  the  spring.  Then  follows  the 
period  of  "autumnal  circulation,"  during  which  the  surface 
and  bottom  strata  have  substantially  the  same  temperature. 
In  December  the  lake  freezes  and  "winter  stagnation" 
begins. 

The  use  of  the  thermophone  for  obtaining  series  of  tem- 
peratures at  frequent  intervals  in  the  vertical  has  enabled  the 
author  to  study  the  temperature  changes  in  more  detail,  and 
to  see  how  they  are  affected  by  the  geography  of  the  lake  and 
the  meteorology  of  the  region. 

In  a  frozen  lake  the  water  in  contact  with  the  under  sur- 


LIMNOLOG  Y. 


6l 


face  of  the  ice  stands  always  at  32°  F.  The  temperature  at 
the  bottom  varies  with  the  depth  and  with  the  meteorological 
conditions  at  the  time  of  freezing.  In  most  lakes,  and  par- 
ticularly in  deep  lakes,  it  stands  at  the  point  of  maximum 
density;  in  shallow  lakes  it  may  be  lower  than  that;  under 
abnormal  conditions,  as  referred  to  on  page  52,  it  may  be 
slightly  higher.  During  the  period  of  winter  stagnation  the 
bottom  temperature  sometimes  rises  very  slightly  on  account 
of  direct  heating  by  the  sun's  rays.  This  is  because  of  the 
diathermancy  of  the  water.  The  temperatures  of  the  water 
between  the  surface  and  the  bottom  are  illustrated  by  Fig.  10. 


50 


55 


DIAGRAM 
SHOWING  THE 

TEMPERATURE 
OF  THE  WATER 

IN  CERTAIN  FROZEN  LAKES. 

OBSERVATIONS  TAKEN 
WITH  THE  THERMOPHONE. 


FIG.  10.     (After  FitzGerald.) 

The  cold  water  is  usually  confined  to  a  thin  layer — seldom 
tnore  than  5  or  10  ft.  thick — under  the  ice,  and  below  that 
layer  the  temperature  changes  but  little  to  the  bottom.  This 
is  shown  by  the  Lake  Cochituate  curve.  This  and  the 


62  THE   MICROSCOPY  OF  DRINKING-WATER. 

(abnormal)  change  in  the  curve  at  the  bottom  may  be 
explained  as  follows:  During  the  period  of  autumnal  circula- 
tion the  temperature  is  uniform  throughout  the  vertical.  As 
the  weather  gets  colder  the  temperature  throughout  the 
vertical  drops.  Until  the  temperature  has  reached  the  point 
of  maximum  density  the  circulation  of  the  water  through  the 
vertical  takes  place  by  thermal  convection.  Below  that  tem- 
perature it  takes  place  chiefly  by  wind  action.  If  the  wind  is 
not  sufficiently  strong  to  induce  complete  circulation  the 
bottom  temperature  ceases  to  fall  at  39.2°.  Thus  the  bottom 
temperature  at  Lake  Cochituate  in  December,  1894,  was  left 
at  that  point.  Later  the  wind  stirred  the  water  to  a  depth  of 
45  ft.,  and  above  that  depth  the  temperature  became  uniform 
at  about  38.5°. 

Freezing  usually  occurs  on  a  cool,  still  night.  The  surface- 
water  cools  and  freezes  before  the  wind  has  had  a  chance  to 
mix  it  with  the  warmer  water  below.  The  suddenness  with 
which  a  lake  freezes  and  the  intensity  of  the  wind  at  the  time 
determine  the  depth  of  the  layer  of  cold  water,  and  the  tem- 
perature of  the  air  and  the  intensity  of  the  wind  previous  to 
the  time  of  freezing  determine  the  temperature  of  the  water 
at  the  bottom.  The  Lake  Winnipesaukee  curve  (Fig.  10) 
represents  the  effect  of  a  current  flowing  between  two  islands. 
A  layer  of  cold  water  about  18  ft.  thick  was  flowing  over  a 
quiet  body  of  warmer  water.  The  dividing  line,  at  a  depth 
of  about  20  ft.,  was  very  sharply  defined.  The  Crystal  Lake 
curve  (Fig.  10)  shows  abnormal  conditions  produced  by 
springs  at  the  bottom  of  the  lake. 

During  the  summer  the  temperature  of  the  water  is  simi- 
larly affected  by  meteorological  conditions.  After  the  ice  has 
broken  up  the  temperature  of  the  water  at  all  depths  rises. 
Above  39.2°  circulation  takes  place  chiefly  by  the  action  of 


LI  M  NO  LOG  Y.  63 

the  wind.  If  there  were  no  wind,  or  if  the  wind  were  not 
sufficient,  the  temperature  at  the  bottom  would  not  rise  above 
39.2°.  In  very  deep  lakes  this  happens,  but  in  most  lakes 
the  wind  causes  it  to  rise  somewhat  above  that  point.  It  con- 
tinues to  rise  as  long  as  the  difference  in  density  between  the 
water  at  the  surface  and  at  the  bottom  does  not  become  too 
great  for  the  wind  to  keep  up  the  circulation.  In  Lake 
Cochituate  this  difference  of  density  is  produced  by  a  differ- 
ence of  about  5°  in  temperature.  When  stagnation  has  once 
begun  the  temperature  at  the  bottom  changes  very  little  dur- 
ing the  summer.  It  sometimes  rises  slightly  on  account  of 
direct  heating,  as  it  does  in  the  winter.  If  warm  weather 
occurs  early  and  suddenly  in  the  spring  the  required  dif- 
ference of  temperature  between  the  upper  and  lower  lay- 
ers is  soon  obtained,  and  consequently  the  temperature 
at  the  bottom  through  the  summer  remains  low.  But  if 
the  season  advances  slowly  the  bottom  temperature  will 
become  fixed  at  a  higher  point.  In  Lake  Cochituate  the 
bottom  temperature  varies  in  different  years  from  42°  to 

45°- 

The  temperatures  of  the  water  between  the  surface  and 
bottom  during  the  summer  may  be  illustrated  by  the  two 
typical  curves  in  Fig.  i  r.  Previous  to  May  13,  1895,  the 
season  had  progressed  gradually.  On  that  day  the  atmos- 
pheric temperature  rose  to  90°  and  there  was  little  wind. 
These  conditions  produced  a  uniform  curve.  Then  followed 
several  days  of  cold,  windy  weather.  The  surface  tempera- 
ture fell  and  the  water  became  stirred  to  a  depth  of  about 
17  ft.  Below  20  ft.,  however,  there  was  little  change. 
These  conditions  usually  continue  through  the  summer,  the 
upper  layers  becoming  warmed  and  stratified,  or  cooled  and 
mixed,  the  lower  layers  remaining  stagnant.  Between  these 


t>4  THE   MICROSCOPY   OF  DRINKING-WATER. 

upper  and  lower  layers  there  is  a  thin  layer  where  the  tem- 
perature changes  rapidly, — sometimes  10°  in  one  vertical  foot. 
This  region  is  sometimes  called  the  thermocline*  Its  position 
and  temperature  gradient  vary  according  to  the  depth  of  the 
lake,  the  intensity  of  the  wind,  and  the  temperature  of  the 
water  above  and  below.  The  upper  boundary  of  the  thermo- 
cline is  sometimes  very  sharp — particularly  in  the  autumn; 
the  lower  boundary  is  less  distinct.  In  the  fall  the  position 


FIG.  ir.  • 

of  the  thermocline  drops  towards  the  bottom  as  circulation 
extends  to  greater  and  greater  depths. 

These  seasonal  changes  of  temperature  are  modified  some- 
what in  very  deep  and  in  very  shallow  lakes  and  in  lakes 
situated  in  extremely  hot  or  cold  climates,  and  these  modifi- 
•cations  may  be  used  as  a  basis  for  classification. 

Classification  of  Lakes  According  to  Temperature. — 
JLakes  may  be  divided  into  three  types,  according  to  their 
surface  temperatures,  and  into  three  orders,  according  to  their 
bottom  temperatures.  The  resulting  nine  classes  are  shown 
in  Fig.  12.  On  these  diagrams  the  boundaries  of  the  shaded 
areas  represent  the  limits  of  the  temperature  fluctuations 
at  different  depths.  The  horizontal  scale  represents  tem- 
peratures in  Fahrenheit  degrees  increasing  towards  the  right, 

*  Suggested  by  Dr.  E.  A.   Birge. 


LIMNOLOG  y. 


and  the  vertical  scale  represents  depth.  The  three  types 
of  lakes  are  designated  as  polar,  temperate,  and  tropical.  In 
lakes  of  the  polar  type  the  surface  temperature  is  never  above 
that  of  maximum  density;  in  lakes  of  the  tropical  type  it  is 
never  below  that  point;  in  lakes  of  the  temperate  type  it  is 


POLAR  TYPE 


TEMPERATE  TYPE 


TROPICAL  TYPE 


1 

1 

FIRST  ORDER 
POLAR  TYPE 

1 

SECOND  ORDER 
POLAR  TYPE 

• 

FIRST  ORDER 
TEMPERATE  TYPE 


FIRST  ORDER 
TROPICAL  TYPE 


SECOND  ORDER 
TEMPERATE  TYPE 


SECOND  ORDER 
TROPICAL  TYPE 


THIRD  ORDER  THIRD  ORDER  THIRD  ORDER 

FIG.  12. — CLASSIFICATION  OF  LAKES  ACCORDING  TO  TEMPERATURE. 

sometimes  below  and  sometimes  above  it.  This  division  into 
types  corresponds  somewhat  closely  with  geographical  loca- 
tion. 

The  three  orders  of  lakes  may  be  defined  as  follows:  lakes 
of  the  first  order  have  bottom  temperatures  which  are  prac- 
tically constant  at  or  very  near  the  point  of  maximum  density; 
lakes  of  the  second  order  have  bottom  temperatures  which 
undergo  annual  fluctuations,  but  which  are  never  very  far 
from  the  point  of  maximum  density;  lakes  of  the  third  order 
have  bottom  temperatures  which  are  seldom  very  far  from  the 
surface  temperatures.  The  division  into  orders  corresponds 


66 


THE   MICROSCOPY   OF  DRINKING-WATER. 


in  a  general  way  to  the  character  of  the  lakes;  i.e.,  their  sizer 
contour,  depth,  surrounding  topography,  etc. 

The  temperature  changes  which  take  place  in  the  nine 
classes  of  lakes  according  to  this  system  of  classification  are 
exhibited  in  another  manner  in  Fig.  13.  These  diagrams 
show  by  curves  the  surface  and  bottom  temperatures  for  each 
season  of  the  year,  the  dates  being  plotted  as  abscissae, 
and  the  temperatures  as  ordinates.  The  shaded  areas  show 
the  difference  between  the  surface  and  bottom  temperatures,. 


POLAR  TYPE 


TEMPERATE  TYPE 


TROPICAL  TYPE 


39.2 
32.0 

^^^^^» 

POLAR  TYPE 


FIRST  ORDER 
TEMPERATE  TYPE 


39.2° 
32.0° 


FIRST  ORDER 
TROPICAL  TYPE 


SECOND  ORDER 
POLAR  TYPE 


SECOND  ORDER 
TEMPERATE  TYPE 


SECOND  ORDER 
TROPICAL  TYPE 


THIRD  ORDER  THIRD  ORDER  THIRD  ORDER 

FIG.   13. — CLASSIFICATION  OF  LAKES  ACCORDING  TO  TEMPERATURE. 

the    wider    the    shaded    area   the   greater    being    the    differ- 
ence. 

A  study  of  these  diagrams  brings  out  some  interesting 
facts  concerning  the  phenomena  of  circulation  and  stagnation. 
In  Fig.  12  it  will  be  seen  that  the  circulation  periods  occur 


LIMNOLOGY.  7 

when  the  curve  showing  the  temperatures  at  various  depths 
becomes  a  vertical  line;  that  is,  when  the  water  all  has  the 
same  temperature.  The  stagnation  periods  are  shown  by  the 
line  being  curved,  the  top  to  the  right  when  the  warmer 
layers  are  above  the  colder,  and  to  the  left  when  the  colder 
layers  are  above  the  warmer.  In  Fig.  13  the  circulation 
periods  are  indicated  by  the  surface  and  bottom  temperature 
curves  coinciding,  and  the  stagnation  periods  by  these  lines 
being  apart.  The  distance  between  the  lines  indicates,  to  a 
certain  extent,  the  difference  in  density  between  the  top  and 
bottom  layers,  and  we  see  that  the  farther  apart  the  lines 
become  the  less  likelihood  there  is  that  the  water  will  be 
stirred  up  by  the  wind. 

In  lakes  of  the  polar  type  there  is  but  one  opportunity  for 
vertical  circulation  (except  in  the  third  order);  namely,  in  the 
summer  season,  when  the  water  approaches  the  temperature 
of  maximum  density.  In  a  lake  of  the  first  order,  that  is,  in 
one  where  the  bottom  temperature  remains  constantly  at 
39.2°,  the  circulation  period  would  be  very  short  indeed,  if 
not  lacking  altogether.  In  a  lake  of  the  second  order  circula- 
tion might  and  probably  would  continue  for  a  longer  period. 
In  a  lake  of  the  third  order  the  water  would  be  in  circulation 
nearly  all  the  time  except  when  frozen.  The  minimum  tem- 
perature limit  indicated  for  this  order,  i.e.,  32°  at  all  depths, 
would  be  possible  only  in  very  shallow  bodies  of  water, 
and  would  simply  indicate  that  all  the  water  was  frozen 
The  temperature  of  the  ice  would  probably  be  below  32° 
at  the  surface.  It  is  probable  that  very  few  polar  lakes 
exist. 

In  lakes  of  the  tropical  type  there  is  likewise  but  one 
period  of  circulation  each  year  (except  in  the  third  order). 
This  would  occur  not  in  summer,  but  in  winter.  In  the  first 


68 


THE   MICROSCOPY   OF  DRINKING-WATER. 


order  this  circulation  period  would  be  brief  or  entirely  want- 
ing; in  the  second  it  would  be  of  longer  duration;  in  the  third 
order  the  water  would  be  liable  to  be  in  circulation  the  greater 
part  of  the  year.  Tropical  lakes  are  quite  numerous,  but 
observations  are  lacking  to  place  them  in  their  proper  order. 
Most  of  the  lakes  of  the  United  States  belong  to  the  tem- 
perate type.  In  this  type  there  are  two  periods  of  circulation 
and  two  periods  of  stagnation  (except  in  the  third  order),  as 
we  have  seen  illustrated  in  the  case  of  Lake  Cochituate.  In 
lakes  of  the  first  order  the  circulation  periods  would  be  very 
short  or  entirely  wanting;  in  the  second  order  the  circulation 
periods  would  be  of  longer  duration ;  in  the  third  order  the 
water  would  be  in  circulation  throughout  the  year  when  the 
surface  was  not  frozen.  The  above  facts  may  be  recapit- 
ulated in  tabular  form  as  follows: 

CIRCULATION    PERIODS. 


Polar  Type. 

Temperate  Type. 

Tropical  Type. 

First  Order. 

One  circulation 
period  possible, 
in  summer,  but 
generally  none. 

Two  circulation 
periods  possible, 
in  spring  and 
fall,  but  gener- 
ally none. 

One  circulation 
period  possible, 
in  winter,  but 
generally  none. 

Second  Order. 

One  circulation 
period,  in  sum- 
mer. 

Two  circulation 
periods,  in 
spring  and 
autumn. 

One  circulation 
period,  in  win- 
ter. 

Third  Order. 

Circulation  at  all 
seasons,  except 
when  surface  is 
frozen. 

Circulation  at  all 
seasons,  except 
when  surface  is 
frozen. 

Circulation  at  all 
seasons. 

Speaking  in  very  general  terms,  one  may  say  that  lakes  of  the  first 
order  have  no  circulation,  lakes  of  the  third  order  have  no  stagnation 
(except  in  winter);  and  lakes  of  the  second  order  have  Both  circulation  and 
stagnation. 


LIMNOLOGY.  69 

In  view  of  the  comparatively  few  series  of  observations  of 
the  temperature  of  our  lakes,  the  author  refrains  from  making 
any  classification  of  the  lakes  of  the  United  States,  but  the 
results  thus  far  obtained  seem  to  indicate  that  the  first  order 
will  include  only  those  lakes  more  than  about  two  hundred 
feet  in  depth,  such,  for  instance,  as  the  Great  Lakes,  Lake 
Champlain,  etc. ;  the  second  order  will  include  those  with 
depths  less  than  about  two  hundred  feet,  but  greater  than 
about  twenty-five  feet;  and  the  third  order  will  include  those 
with  depths  less  than  twenty-five  feet.  These  boundaries 
are  only  approximate,  and  it  should  be  remembered  that 
depth  is  not  the  only  factor  which  influences  the  bottom  tem- 
perature. 

Stagnation  is  sometimes  observed  in  small  artificial  reser- 
voirs even  when  the  depth  is  less  than  twenty  feet.  It  is 
usually  of  short  duration. 

TRANSMISSION  OF  LIGHT  BY  WATER. 

The  amount  of  light  received  by  the  micro-organisms  in 
a  lake  depends  upon  the  intensity  of  the  light  at  the  surface 
of  the  water  and  upon  the  extent  to  which  the  light  is  trans- 
mitted by  the  water.  The  transmission  of  light  by  water 
varies  chiefly  with  the  amount  of  dissolved  and  suspended 
matter  that  it  contains.  The  former  affects  its  coefficient  of 
absorption;  the  latter  acts  as  a  screen  to  shut  out  the  light. 
In  studying  the  penetration  of  light  into  a  body  of  water  it 
is  necessary  to  take  account  of  its  color  and  its  turbidity. 

Color  of  Water. — Some  surface-waters  are  colorless,  but 
in  most  ponds  and  lakes  the  water  has  a  more  or  less  pro- 
nounced brownish  color.  This  may  be  so  slight  as  to  be 
hardly  preceptible,  or  it  may  be  as  dark  as  that  of  weak  tea. 
It  is  darkest  in  water  draining  from  swamps,  and  the  color  of 


i 


70  THE   MICROSCOPY   OF  DRINKING-WATER. 

the  water  in  any  pond  or  stream  bears  a  close  relation  to  the 
amount  of  swamp-land  upon  the  tributary  watershed. 

The  color  is  due  to  dissolved  substances  of  vegetable 
origin  extracted  from  leaves,  peaty  matter,  etc.  It  is  quite 
as  harmless  as  tea.  The  exact  chemical  nature  of  the  color- 
ing matter  is  not  known.  It  is  complex  in  composition. 
Tannins,  glucosides,  and  their  derivatives  are  doubtless 
present.  The  color  of  a  water  usually  bears  a  close  relation 
to  the  albuminoid  ammonia  present.  Carbon,  however,  is 
the  important  element  in  its  composition.  The  color  of  a 
water  varies  very  closely  with  the  "oxygen  consumed." 
Iron  is  usually  present,  and  its  amount  varies  with  the  depth 
of  the  color.  In  some  waters  iron  alone  imparts  a  high  color, 
but  in  peaty  waters  it  plays  a  subsidiary  part. 

The  color  of  a  water  is  usually  stated  in  figures  based  on 
comparisons  made  with  some  arbitrary  standard,  the  figures 
increasing  with  the  depth  of  the  color.  The  Platinum-Cobalt 
Standard,  the  Natural  Water  Standard,  and  the  Nessler 
Standard  are  those  most  commonly  used.  The  first  is  the 
generally  accepted  standard.  Comparisons  of  the  water  with 
the  standard  may  be  made  in  tall  glass  tubes  or  in  a  colorim- 
eter such  as  that  used  at  the  Boston  Water  Works  * 

For  field-work  a  color  comparator,  by  which  the  color  of 
the  water  is  compared  with  disks  of  colored  glass,  is  very  use- 
ful. The  water  is  placed  in  a  metallic  tube  with  glass  ends 
and  its  color  compared  with  a  second  tube  containing  distilled 
water  and  with  one  end  covered  with  one  or  more  of  the  glass 
disks.  This  apparatus,  devised  for  the  United  States  Geolog- 
ical Survey  by  Mr.  Allan  Hazen  and  the  author,  is  illustrated 
in  Fig.  14. 

*  See   FitzGerald   and    Foss,  "On   the   Color  of   Water."    Jour.    Frank. 
Inst.,  Dec.  1894. 


LIMN O LOG  Y. 


•01 
U.  S.  Geological  Survey  Apparatus  for  Measuring  the  Color  of  Water. 


100- 

110— 
120- 


m 


U.  S.  Geological  Survey  Turbidity  Rod. 
FIG.  14. 


72  THE   MICROSCOPY   OF  DRINKING-WATER. 

The  amount  of  color  in  the  water  collected  from  a  water- 

• 

shed  has  a  seasonal  variation.  This  may  be  illustrated  by 
the  color  of  the  water  in  Cold  Spring  Brook,  at  the  head  of 
Basin  No.  4,  Boston  Water  Works.  This  brook  is  fed  in  part 
from  several  large  swamps.  The  figures  given  are  based  on 
weekly  observations. 

AVERAGE   COLOR    OF    WATER    IN    COLD    SPRING    BROOK,  1894. 
Jan.     Feb.     Mar.    Apr.      May.     June.     July.    Aug.    Sept.     Oct.      Nov.      Dec.  Av. 

.99     .88     .96     .93     1.42     1.59     .98     .75     .60     .69     1.44     1.20        1.04 

There  are  usually  two  well-defined  maxima,  one  in  May 
or  June  and  one  in  November  or  December.  In  the  winter 
and  early  spring  the  color  of  the  water  is  low  because  of 
dilution  by  the  melted  snow.  As  the  yield  of  the  watershed 
diminishes  the  color  increases  until  the  water  standing  in  the 
swamp  areas  ceases  to  be  discharged  into  the  stream.  During 
the  summer  the  water  in  the  swamps  is  high-colored,  but  its 
effect  is  not  felt  in  the  stream  until  the  swamps  overflow  in 
the  fall.  Heavy  rains  during  the  summer  may  cause  the 
swamps  to  discharge  and  increase  the  color  of  the  water  in 
the  reservoirs  below.  It  has  been  found  that  in  general  the 
color  of  the  water  delivered  from  any  watershed  bears  a  close 
relation  to  the  rainfall.  In  some  localities  this  is  more  notice- 
able than  in  others.  In  Massapequa  Pond  of  the  Brooklyn 
water-supply  the  color  varies  greatly  from  week  to  week,  and 
the  fluctuations  are  almost  exactly  proportional  to  the  rain- 
fall. In  large  bodies  of  water  the  seasonal  fluctuations  in 
color  are  less  pronounced. 

The  hue  of  the  water  in  the  autumn  is  somewhat  different 
from  that  in  the  spring.  The  fresh- fallen  leaves  and  vege- 
table matter  give  a  greenish-brown  color  that  is  quite  different 
from  the  reddish-brown  color  produced  from  old  peat. 


LIMNOLOGY  73 

When  colored  water  is  exposed  to  the  light  it  becomes 
bleached.  An  elaborate  series  of  experiments  made  at  the  Bos- 
ton Water  Works  by  exposing  bottles  of  high-colored  water 
to  direct  sunlight  for  known  periods  showed  that  during  100 
hours  of  bright  sunlight  the  color  was  reduced  about  20$,  and 
that  with  sufficient  exposure  all  the  color  might  be  removed. 
The  bleaching  action  was  found  to  be  independent  of  tem- 
perature. Sedimentation  had  but  little  influence  on  it.  It 
was  dependent  entirely  upon  the  amount  of  sunlight.  The 
percentage  reduction  was  independent  of  the  original  color  of 
the  water. 

This  bleaching  action  takes  place  in  reservoirs  where 
colored  water  is  stored.  Stearns  has  stated  that  in  an  unused 
reservoir  20  ft.  deep  the  color  of  the  water  decreased  from 
.40  to  .10  in  six  months.  In  Basin  No.  4,  referred  to  above, 
the  average  color  of  the  water  in  the  influent  stream  for  the 
year  1894  was  1.04.  For  the  same  year  the  average  color  of 
the  water  at  the  lower  end  of  the  basin  was  .71.  It  should 
be  stated  that  this  difference  is  not  due  wholly  to  bleaching 
action.  The  amount  of  coloring-matter  entering  the  reservoir 
is  not  shown  by  the  figure  1.04,  for  the  reason  that  the 
quantity  of  water  flowing  in  the  stream  is  not  uniform.  It  is 
greatest  in  the  spring  when  the  melting  snows  give  the  water 
a  color  lower  than  the  average.  Furthermore,  some  colorless 
rain-water  and  ground-water  enters  the  basin.  There  is  also 
a  loss  of  high-colored  water  at  the  wasteway  at  a  season  when 
the  color  of  the  water  is  above  the  average.  It  is  a  difficult 
matter  to  ascertain  just  the  amount  of  bleaching  action  that 
takes  place  in  a  reservoir  through  which  water  is  constantly 
flowing. 

Experiments  (by  the  author)  made  by  exposing  bottles  of 
colored  water  at  various  depths  in  reservoirs  have  shown  that 


74  THE   MICROSCOPY   OF  DRINKING-WATER. 

the  bleaching  action  that  takes  place  at  the  surface  of  a 
reservoir  is  considerable, — sometimes  50$  in  a  month,  It 
-decreases  rapidly  with  increasing  depth,  and  the  rapidity  with 
which  it  decreases  below  the  surface  depends  upon  the  color 
of  the  water  in  the  reservoir,  as  the  table  on  the  following 
page  will  show. 

From  these  and  many  similar  experiments  it  has  been 
found  possible  to  calculate  the  extent  of  the  bleaching  action 
that  takes  place  in  any  reservoir.  The  results  agree  closely 
with  the  observed  color-readings  of  the  water  in  the  reservoir. 
The  experiments  also  bear  directly  upon  the  point  under 
•discussion,  namely,  the  penetration  of  light  into  the  water 
of  a  reservoir. 

EXPERIMENTS  TO  DETERMINE  THE  AMOUNT  OF  BLEACHING 
ACTION    AT   DIFFERENT    DEPTHS. 

Expt.  No.  i.  Expi.  No.  2.  Rxpt.  No   3. 

Color  of  water  in  reservoir 20  37  44 

Time  of  exposure.          Aug.  6-Sept.  4  May  5-June  4   July  2-Aug.  3 

Color  of  water  exposed    175  272  170 

Percentage  reduction  of  color: 

At  depth  of    o.o    ft 52$  41$ 

"     0.5     " t$%  23%  2o% 

11       "     1.25  " 32$  Bfo  12% 

"       "       "25     " 2i#  4%  4* 

"       "     5.0    "  14$  4$  3# 

"       "       "     7-5     " 3#  o#  °% 

"          "          "    10.0      " 1%  0%  0% 

•<       "       "   15.0    " 0%  0%  0% 

Dark  room o%  o%  o% 

Turbidity  of  Water. — The  turbidity  of  water  is  due  to  the 
presence  of  particles  of  matter  in  suspension,  such  as  clay,  silt, 
finely  divided  organic  matter,  microscopic  organisms,  etc. 

There  are  three  principal  methods  used  for  measuring  tur- 
bidity which  give  fairly  comparable  results.  These  are:  i,  Com- 
parison with  silica  standards;  2,  Platinum- wire  method;  3,  Tur- 


LIMNOLOGY.  75 

bidimeter  method.  In  all  cases  the  results  of  the  observations 
are  expressed  in  numbers  which  correspond  to  turbidities  pro- 
duced by  equivalent  amounts  of  finely-divided  silica  in  parts 
per  million. 

The  standard  of  turbidity  has  been  defined  by  the  U.  S.  Geo- 
logical Survey  as  follows : 

"  The  standard  of  turbidity  shall  be  a  water  which  contains 
ico  parts  of  silica  per  million  in  such  a  state  of  fineness  that  a 
bright  platinum  wire  i  millimeter  in  diameter  can  just  be  seen 
when  the  center  of  the  wire  is  100  millimeters  below  the  surface 
of  the  water  and  the  eye  of  the  observer  is  1.2  meters  above  the 
wire,  the  observation  being  made  in  the  middle  of  the  day,  in 
the  open  air,  but  not  in  sunlight,  and  in  a  vessel  so  large  that 
the  sides  do  not  shut  out  the  light  so  as  to  influence  the  results. 
The  turbidity  of  such  water  shall  be  100." 

The  most  convenient  method  for  limnological  field-work  is 
the  platinum-wire  method.  This  method  requires  a  rod  with 
platinum  wire  of  a  diameter  of  one  mm.  or  0.04  inches,  inserted 
in  it  about  one  inch  from  the  end  of  the  rod  and  projecting  from 
it  at  least  one  inch  at  a  right  angle.  Near  the  end  of  the  rod,  at 
a  distance  of  1.2  meters  (about  four  feet)  from  the  platinum  wire, 
a  wire  ring  is  placed  directly  above  the  wire,  through  which, 
with  his  eye  directly  above  the  ring,  the  observer  looks  in  mak- 
ing the  examination.  The  rod  is  graduated  as  follows: 

The  graduation  mark  of  100  is  placed  on  the  rod  at  a  distance 
of  ico  mm.  from  the  centre  of  the  wire.  Other  graduations  are 
made  according  to  the  following  table,  which  is  based  on  the 
best  obtainable  data  and  in  which  the  distances  are  intended  to 
be  such  that  when  the  water  is  diluted  the  turbidity  readings 
will  decrease  in  the  same  proportion  as  the  percentage  of  the 
original  water  in  the  mixture.  These  graduations  are  those  used 
to  construct  what  is  known  as  the  U.  S.  Geological  Survey 
Turbidity  Rod  of  1902.  (See  Fig.  14.) 


76 


THE   MICROSCOP  Y  OF  DRINKING-  WA  TER. 


Turbidity, 
Parts  per 
Million. 

Vanishing 
Depth  of 
Wire,  mm. 

Turbidity, 
Parts  per 
Million. 

Vanishing 
Depth  of 
Wire,  mm. 

Turbidity, 
Parts  per 
Million. 

Vanishing 
Depth  of 
Wire,  mm. 

7 

I095 

28 

314 

1  2O 

86 

8 

971 

30 

296 

130 

81 

9 

873 

35 

257 

140 

76 

10 

794 

40 

228 

150 

72 

ii 

729 

45 

205 

160 

68.7 

12 

674 

50 

l87 

1  80 

62.4 

13 

627 

55 

171 

200 

57-4 

14 

587 

60 

158 

250 

49.1 

15 

55i 

65 

147 

300 

43-2 

16 

520 

70 

138 

35<> 

38.8 

i? 

493 

75 

130 

400 

35-4 

18 

468 

80 

122 

500 

30-9 

J9 

446 

85 

Tl6 

600 

27.7 

20 

426 

9° 

no 

800 

23-4 

22 

391 

95 

t°5 

IOOO 

20.9 

24 

361 

100 

IOO 

1500 

17.! 

26 

336 

no 

93 

200O 

14-8 

3OOO 

12.  I 

Procedure. — Push  the  rod  vertically  down  into  the  water  as  far 
as  the  wire  can  be  seen,  and  then  read  the  level  of  the  surface  of 
the  water  on  the  graduated  scale.  This  will  indicate  the  turbidity. 

The  following  precautions  should  be  taken  to  insure  correct 
results : 

Observations  should  be  made  in  the  open  air,  preferably  in  the 
middle  of  the  day  and  not  in  direct  sunlight.  The  wire  should 
be  kept  bright  and  clean.  If  for  any  reason  observations  cannot 
be  made  directly  under  natural  conditions  a  pail  or  tank  may 
be  filled  with  water  and  the  observation  taken  in  that,  but  in  this 
case  care  should  be  taken  that  the  water  is  thoroughly  stirred 
before  the  observation  is  made,  and  no  vessel  should  be  used  for 
this  purpose  unless  its  diameter  is  at  least  twice  as  great  as  the 
depth  to  which  the  wire  is  immersed.  Waters  which  have  a  tur- 
bidity above  500  should  be  diluted  with  clear  water,  before 
the  observations  are  made,  but  in  case  this  is  done  the  degree 
of  dilution  used  should  be  stated  and  form  a  part  of  the  report. 

For  very  clear  waters  the  use  of  a  black-and-white  disk,  as 
suggested  beyond,  will  be  found  more  satisfactory  than  that  of 
the  platinum  wire. 


LTMNOLOG  Y.  77 

The  most  complete  studies  of  the  transparency  of  large 
bodies  of  water  were  those  made  by  Forel  and  others  in 
Switzerland.  Three  methods  of  experiment  were  employed. 
The  first  was  that  of  the  visibility  of  plates.  This  method, 
used  by  Secchi  in  1865  in  determining  the  transparency  of 
the  water  in  the  Mediterranean  Sea,  consisted  of  lowering  a 
white  disc  (20  cm.  in  diameter)  into  the  water  and  noting  the 
•depth  at  which  it  disappeared  from  view,  and  then  raising  it 
and  noting  the  point  at  which  it  reappeared.  The  mean  of 
these  two  depths  was  called  the  limit  of  visibility.  The 
second  method,  known  as  that  of  the  Genevan  Commission, 
was  similar  to  the  first,  but  instead  of  a  white  disc  an  incan- 
descent lamp  was  lowered  into  the  water.  This  light  when 
seen  through  the  water  from  above  presented  an  appearance 
similar  to  that  of  a  street-lamp  in  a  fog;  that  is,  there  was  a 
bright  spot  surrounded  by  a  halo  of  diffused  light.  When  the 
light  was  lowered  into  the  water  the  bright  spot  first  dis- 
appeared from  view.  The  depth  of  this  point  was  noted  as 
the  "  limit  of  clear  vision."  Finally  the  diffused  light  dis- 
appeared, and  the  depth  of  this  point  was  called  the  "  limit 
of  diffused  light."  Both  these  methods  were  useful  only  in 
comparing  the  relative  transparency  of  different  waters  or  of 
the  same  water  at  different  times.  In  order  to  get  an  idea  of 
the  intensity  of  light  at  different  depths  a  photographic 
method. was  used.  Sheets  of  sensitized  albumen  paper  were 
mounted  in  a  frame  in  such  a  way  that  half  of  the  sheet  was 
covered  with  a  black  screen,  while  the  other  half  was  exposed. 
A  series  of  these  papers  was  attached  to  a  rope  and  lowered 
into  the  water;  they  were  equidistant  and  so  supported  that 
they  assumed  a  horizontal  position  in  the  water.  They  were 
placed  in  position  in  the  night  and  allowed  to  remain  24 


78  THE   MICROSCOPY   OF  DRINKING-WATER. 

hours.  On  the  next  night  they  were  drawn  up  and  placed  in 
a  toning-bath.  A  comparison  of  prints  made  at  different 
depths  enabled  the  observer  to  determine  the  depth  at  which 
the  light  ceased  to  affect  the  paper  and  to  obtain  an  idea  of 
the  relative  intensity  of  the  light  at  different  depths.  To 
assist  in  this  comparison  an  arbitrary  scale  was  made  by 
exposing  sheets  of  the  same  paper  to  bright  sunlight  for 
different  lengths  of  time. 

The   results   of   the   experiments   are   given   by  Forel   as 
follows: 

In  Lake  Geneva  the  limit  of  visibility  of  a  white  disk  20 
cm.  in  diameter  was  21  m.  The  limit  of  clear  vision  of  a 
7-candle-power  incandescent  lamp  was  40  m.  ;  the  limit  of 
diffused  light  was  about  90  m.  The  depth  at  which  the  light 
ceased  to  affect  the  photographic  paper  was  100  m.,  when  the 
paper  was  sensitized  with  chloride  of  silver,  and  about  200  m. 
when  sensitized  with  iodobromide  of  silver.  These  depths 
were  less  in  summer  than  in  winter  on  account  of  the  increased 
turbidity  of  the  water.  The  transparency  of  the  water  in 
other  lakes,  as  shown  by  the  limit  of  visibility  of  a  white  disk,. 
is  cited  as  follows:  Lake  Tahoe,  33  m. ;  La  Mer  des  Antilles, 
50  m. ;  Lac  Lucal,  60  m. ;  Mediterranean  Sea,  42.5  m. ; 
Pacific  Ocean,  59  m.  It  should  be  remembered  that  these 
are  all  comparatively  clear  and  light-colored  waters,  and  that 
in  them  the  light  penetrates  to  far  greater  detph  than  in 
turbid  and  colored  water.  For  example,  in  Chestnut  Hill 
Reservoir,  a  disc  lowered  into  the  water  at  a  time  when  the 
color  was  0.92  disappeared  from  view  at  a  depth  of  six  feet. 

The  author's  experiments  have  shown  that  the  limit  of 
visibility  may  be  determined  most  accurately  by  using  a  disc 
about  8  inches  in  diameter,  divided  into  quadrants  painted 


LIMNOLOGY.  79 

alternately  black  and  white  like  the  target  of  a  level-rod,  and 
looking  vertically  down  upon  it  through  a  water-telescope 
provided  with  a  suitable  sunshade.  It  has  been  found  that 
the  limit  of  visibility  obtained  in  this  manner  bears  a  close 
relation  to  the  turbidity  of  the  water  as  determined  by  a 
turbidimeter.  It  also  varies  with  the  color  of  the  water,  but 
the  relation  has  not  been  carefully  worked  out. 

Absorption  of  Light  by  Water. — The  absorption  of  light 
by  distilled  water  is  said  to  vary  with  the  temperature.  The 
following  coefficients  are  given  by  Wild  as  the  result  of 
laboratory  experiments.  It  seems  probable  that  the  figures 
are  too  low.  • 

Temperature.  Intensity  of  Light  after  passing 

through  i  dm.  of  Distilled  Water. 

24.4°  C.  0.9179 

17.0  0.93968 

6.2  0.94769 

The  coefficient  of  absorption  of  light  by  colored  water  is 
quite  unknown. 

The  reduction  of  light  in  passing  downward  through  a 
body  of  water  is  supposed  to  follow  the  law  that  as  the  depth 
increases  arithmetically  the  intensity  of  the  light  decreases 
geometrically.  For  example,  if  the  intensity  of  the  light 
falling  upon  the  surface  of  a  pond  is  represented  by  I,  and  if 
J  of  the  light  is  absorbed  by  the  first  foot  of  water  (some 
colored  waters  absorb  even  more  than  this),  then  the  intensity 
of  light  at  the  depth  of  I  ft.  will  be  f ;  the  second  foot  of 
water  will  absorb  \  of  f,  and  the  intensity  at  the  depth  of 
2  ft.  will  be  T9^;  and  so  on.  At  this  rate  of  decrease  the 
intensity  of  light  at  a  depth  of  10  ft.  will  be  only  about  5$  of 
that  at  the  surface. 


SO  THE   MICROSCOPY   OF  DRINKING-WATER. 

There  are  few  accurate  data  extant  regarding  the  quality 
of  the  light  at  different  depths,  but  theory  would  lead  us  to 
infer  that  in  passing  downward  from  the  surface  to  the 
bottom  of  a  lake  the  light  varies  considerably  in  character. 
It  is  said  that  the  red  and  yellow  rays  are  most  readily  trans- 
mitted. 


CHAPTER  VI. 

GEOGRAPHICAL   DISTRIBUTION   OF   MICROSCOPIC 
ORGANISMS   IN   PONDS   AND   LAKES. 

THE  microscopic  organisms  that  are  found  most  commonly 
in  water-supplies  taken  from  lakes  or  storage  reservoirs  are 
given  in  the  following  table,*  arranged  according  to  the  usual 
system  of  classification  and  divided  into  groups  according  to 
their  abundance  and  frequency  of  occurrence.  The  first  group 
includes  those  genera  which,  in  their  season,  are  often  found 
in  large  numbers;  the  second  group  includes  those  which  are 
found  but  occasionally  in  large  numbers;  the  third,  those 
which  often  occur  in  small  numbers;  the  fourth,  those  which 
are  rarely  observed.  This  division,  while  not  wholly  satisfac- 
tory, enables  one  to  separate  the  important  from  the  unim- 
portant forms.  As  observations  multiply,  the  list  may  be 
extended  and  some  genera  may  be  changed  from  one  group 
to  another.  The  organisms  printed  in  heavy  type  have  given 
trouble  in  water-supplies,  either  by  producing  odors  or  by 
making  the  water  turbid  and  unsuitable  for  laundry  purposes. 

DIATOMACE^:. 

Commonly  found  in  large  numbers.  Asterionella,  Cyclo- 
tella,  Melosira,  Synedra,  Tabellaria. 

Occasionally  found  in  large  numbers.  Diatoma,  Fragilaria, 
Nitzschia,  Stephanodiscus. 

*  Compiled  from  published  biological  examinations  of  Massachusetts 
water-supplies. 

81 


82  THE   MICROSCOPY   OF  DRINKING- WATER. 

Commonly  found  in  small  numbers.  Epithemia,  Gom- 
phonema,  Navicula,  Stauroneis. 

Occasionally  observed.  Achnanthes,  Amphiprora,  Am- 
phora, Bacillaria,  Cocconeis,  Cocconema,  Cymbella,  Diades- 
mis,  Encyonema,  Eunotia,  Grammatophora,  Himantidium, 
Isthmia,  Meridion,  Odontidium,  Orthosira,  Pinnularia,  Pleuro- 
sigma,  Schizonema,  Striatella,  Surirella,  Tetracyclus. 

CHLOROPHYCE^E. 

Commonly  found  in  large  numbers.  Chlorococcus,  Pro- 
tococcus,  Scenedesmus. 

Occasionally  found  in  large  numbers.  Ccelastrum,  Cos- 
marium,  Palmella,  Pandorina,  Polyedrium,  Raphidium,, 
Staurastrum,  Volvox.  '.  ' 

Commonly  found  in  small  numbers.  Closterium,  Conferva, 
Desmidium,  Euastrum,  Eudorina,  Gonium,  Micrasterias, 
Ophiocytium,  Pediastrum,  Sphaerozosma,  Staurogenia,  Tetra- 
spora,' Ulothrix,  Xanthidium. 

Occasionally  observed.  Arthrodesmus,  Bambusina,  Botryo- 
coccus,  Characium,  Chaetophora,  Cladophora,  Dactylococcus, 
Dictyosphserium,  Dimorphococcus,  Draparnaldia,  Gloeocystis, 
Hyalotheca,  Mesocarpus,  Nephrocytium,  Penium,  Selenas- 
trum,  Sorastrum,  Spirogyra,  Stigeoclonium,  Tetmemorus, 
Zygnema. 

CYANOPHYCE^:. 

Commonly  found  in  large  numbers.  Anabsena,  Clathro* 
cystis,  Coelosphaerium,  Microcystis. 

Occasionally  found  in  large  numbers.  Aphanizomenon, 
Chroococcus,  Oscillaria. 

Commonly  found  in  small  numbers.     Aphanocapsa. 

Occasionally  observed.  Gloeocapsa,  Lyngbya,  Merismope- 
dia,  Microcoleus,  Nostoc,  Rivularia,  Sirosiphon,  Tetrapedia., 


GEOGRAPHICAL    DISTRIBUTION   OF  ORGANISMS.         83 

SCHIZOMYCETES   AND    FUNGI. 

Commonly  found  in  large  numbers.      Crenothrix. 

Occasionally  found  in  large  numbers.      Cladothrix. 

Commonly  found  in  small  numbers.  Beggiatoa,  Lepto- 
thrix,  Molds. 

Occasionally  observed.  Achlya,  Leptomitus,  Saprolegnia, 
Sarcina,  Spirillum. 

PROTOZOA. 

Commonly  found  in  large  numbers.  Cryptomonas,  Dino- 
bryon,  Peridinium,  Synura,  Uroglena. 

Occasionally  found  in  large  mimbers.  Bursaria,  Chloro- 
monas,  Glenodinium,  Mallomonas,  Raphidomonas. 

Commonly  found  in  small  numbers.  Actinophrys,  Amoeba, 
Anthophysa,  Ceratium,  Cercomonas,  Codonella,  Epistylis, 
Monas,  Tintinnus,  Trachelomonas,  Vorticella. 

Occasionally  observed.  Acineta,  Arcella,  Chlamydomonas, 
Coleps,  Colpidium,  Cyphodera,  Difflugia,  Enchelys,  Euglena, 
Euglypha,  Euplotes,  Glaucoma,  Halteria,  Heteronema,  Nas- 
sula,  Paramaecium,  Phacus,  Pleuronema,  Raphidodendron, 
Stentor,  Syncrypta,  Trichodina,  Uvella,  Zoothamnium. 

ROTIFERA. 

Commonly  found  in  small  numbers.  Anuraea,  Conochilus, 
Polyarthra,  Rotifera,  Synchaeta. 

Occasionally  observed.  Asplanchna,  Colurus,  Eosphora, 
Floscularia,  Lacinularia,  Mastigocerca,  Microcodon,  Mono- 
cerca,  Monostyla,  Noteus,  Sacculus,  Triarthra. 

CRUSTACEA. 

Commonly  found  in  small  numbers.  Bosmina,  Cyclops, 
Daphnia. 

Occasionally  observed.     Alona,  Cypris,  Diaptomus,  Sida. 


84  THE   MICROSCOPY   OF  DRINKING-WATER. 

MISCELLANEOUS. 

Occasionally  observed.  Acarina,  Anguillula,  Batracho- 
spermum,  Chaetonotus,  Gordius,  Hydra,  Macrobiotus,  Mey- 
enia,  Nais,  Spongilla;  besides  spores,  ova,  insect  scales, 
pollen-grains,  vegetable  fibres  and  tissue,  yeast-cells,  starch- 
grains,  etc. 

The  above  may  be  summarized  numerically  as  follows: 


Classification. 

Number  of  Genera. 

Commonly 
found 
in  large 
numbers. 

Occasion- 
ally found 
in  large 
numbers. 

Commonly 
found 
in  small 
numbers. 

Occasion- 
ally 
observed. 

Total. 

5 
3 
4 

i 
5 

0 

o 
o 

4 
8 

3 

I 

5 
o 
o 
o 

4 
14 

I 

3 
ii 

5 
3 
o 

22 
21 

8 

5 
24 

12 

4 

IO 

35 
46 
16 

10 

45 
17 
7 

IO 

Fungi  and  Schizomycetes 

Total  

18 

21 

4i 

1  06 

1  86 

It  will  be  observed  that  186  genera  have  been  recorded, 
— 108  plants  and  78  animals.  Of  these  only  18  are  com- 
monly found  in  large  numbers, — 13  plants  and  5  animals. 
21  more  are  occasionally  found  in  large  numbers, — 16  plants 
and  5  animals.  41  genera  are  frequently  seen  in  small 
numbers,  while  106  genera,  or  more  than  one  half  of  all 
are  seen  occasionally,  some  of  them  rarely.  The  most, 
important  classes  are  the  Diatomaceae,  Chlorophyceae,  Cyano- 
phyceae,  and  Protozoa,  as  shown  by  the  large  number  of 
genera  and  by  their  greater  abundance.  Furthermore,  these 
classes  include  all  but  one  of  the  most  troublesome  genera 
that  have  been  found  in  large  numbers.  10  genera  may  be 


GEOGRAPHICAL   DISTRIBUTION  OF  ORGANISMS.        .85 

said  to  be  very  troublesome  because  of  their  wide  distribution, 
the  frequency  of  their  occurrence,  and  their  unpleasant  effects. 
They  are  Asterionella,  Anabaena,  Clathrocystis,  Coelosphae- 
rium,  Aphanizomenon,*  Dinobryon,  Peridinium,  Synura, 
Uroglena,  and  Glenodinium.  This  list  seems  like  a  short  one 
when  one  considers  the  annoyance  that  the  microscopic 
organisms  have  caused  in  various  water-supplies. 

The  observations  of  sanitarians  and  the  planktologists  show 
that  the  microscopic  organisms  are  very  widely  distributed 
in  nature.  They  are  found  in  all  parts  of  the  world,  and 
under  great  varieties  of  climatic  conditions.  It  is  probable 
that  they  appeared  on  the  earth  at  an  early  geological  age. 
Some  of  them  are  found  as  fossils, — notably  the  diatoms, 
which  have  silicious  walls  that  are  almost  indestructible. 

In  spite  of  the  vast  amount  of  study  that  has  been  given 
to  the  microscopic  organisms  we  are  still  very  far  from  under- 
standing the  laws  governing  their  distribution.  Why  it  is 
that  a  certain  genus  v/ill  grow  vigorously  in  one  pond  and  at 
the  same  time  be  absent  from  a  neighboring  one  where  the 
conditions  apparently  are  as  favorable,  or  why  a  form  may 
suddenly  appear  in  a  pond  where  it  has  been  never  before 
seen,  we  are  still  unable  to  say  with  certainty.  Solution  of 
such  problems  involves  a  far-reaching  knowledge  of  the 
chemical  constituents  and  the  life-history  of  the  organisms, 
besides  the  effect  of  physical  conditions,  such  as  temperature, 
pressure,  light,  etc.  The  sciences  of  bio-chemistry  and  bio- 
physics are  yet  in  their  infancy.  Until  these  have  been 
further  developed  many  problems  connected  with  the  micro- 
scopic organisms  must  remain  unsolved. 

The  following  statistics  are  of  some  value  in  connection 

*  In  the  reports  of  the  Massachusetts  State  Board  of  Health  this  organ- 
ism is  sometimes  classed  with  Oscillaria. 


"86 


THE   MICROSCOPY  OF  DRINKING-WATER. 


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GEOGRAPHICAL    DISTRIBUTION   OF   OKGANISMS. 


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88  THE  MICROSCOPY  OF  DRINKING-WATER. 

with  this  subject,  as  they  show  the  relative  abundance  of  the 
different  classes  of  organisms  in  some  of  the  important  surface- 
water  supplies  of  Massachusetts,  together  with  some  of  the 
elements  of  the  sanitary  chemical  analysis. 

For  the  purpose  of  this  comparison  57  ponds  and  reser 
voirs  were  selected  where  monthly  examinations,  both  chemi- 
cal and  biological,  have  been  carried  on  for  a  number  of  years 
by  the  State  Hoard  of  Health.  The  results  of  these  exami- 
nations were  carefully  studied,  and  the  ponds  (which,  for 
convenience,  we  may  consider  to  include  lakes,  ponds,  and 
storage  reservoirs)  divided  into  groups  as  shown  in  the  table 
on  pages  82  and  83. 

The  first  two  columns  in  this  table  give  the  names  of  the 
ponds  and  the  cities  which  they  supply.  The  third  gives  the 
depth  of  the  pond,  whether  shallow  or  deep.  The  next  four 
columns  show  the  relative  abundance  of  the  four  most  im- 
portant classes  of  organisms;  namely,  the  Diatomaceae, 
Chlorophyceae,  Cyanophyceae,  and  Protozoa.  The  four 
groups  are  characterized  as  follows:  the  group  to  which  each 
pond  belongs  is  indicated  by  a  Roman  numeral. 

Group  I.  Number  of  organisms  often  as  high  as  1000 
per  c.c. 

Group  II.  Number  of  organisms  only  occasionally  as  high 
as  1000  per  c.c. 

Group  III.  Number  of  organisms  ordinarily  between  100 
and  500  per  c.c. 

Group  IV.  Number  of  organisms  never  above  100  per  c.c. 

These  figures  refer  not  to  the  numbers  present  in  the 
average  sample  of  water,  but  to  the  numbers  during  the 
season  of  maximum  growth.  The  boundaries  of  the  groups 
were  not  sharply  defined,  and  in  a  number  of  cases  it  was 
hard  to  tell  whether  a  pond  should  be  classed  in  group  II  or 


GEORAPHICAL   DISTRIBUTION  OF  ORGANISMS. 


III.  The  last  five  columns  show  the  ponds  divided  into 
classes  according  to  some  of  the  elements  of  the  chemical 
analysis;  namely,  color,  excess  of  chlorine,  hardness,  albumi- 
noid ammonia  (in  solution),  free  ammonia,  and  nitrates  In 
each  case  four  classes  are  given,  division  being  made  accord- 
ing to  the  schedule  given  at  the  bottom  of  the  table. 

If  we  consider  the  ponds  with  reference  to  the  growths  of 
organisms,  we  obtain  from  the  above  table  the  following 
summary: 


Group. 

Number  per  c.c. 

Number  of  Ponds  and  Reservoirs. 

Diato- 
maceae. 

Chloro- 
phyceae. 

Cyano- 
phyceae. 

Protozoa. 

I 
II 
III 
IV 

24 
8 

1 

5 

II 
29 

12 

7 

10 

18 

22 

8 
7 
35 
7 

Occasionally  above  1000  per  c.c  
Usually  between  100  and  500  per  c.c.  . 

From  this  it  appears  that  the  Diatomaceae  are  the  organ- 
isms most  commonly  found  in  large  numbers.  There  are  24. 
ponds  (42$  of  the  ponds  considered)  which  often  have  these 
organisms  as  high  as  1000  per  c.c.,  while  in  only  6  (11$)  are 
they  always  below  100  per  c.c.  The  Chlorophyceae  are  not 
often  found  in  great  abundance,  though  many  ponds  contain 
them  in  moderate  numbers.  Only  5  ponds  (9$)  have  growths 
of  1000  per  c.c.,  while  29  (70$)  have  growths  of  from  100  to 
500  per  c.c.  The  Cyanophyceae  are  not  as  common  as  the 
Chlorophyceae,  but  where  they  do  occur  their  growth  is  usually 
greater  and  they  cause  more  trouble.  There  are  7  ponds 
(12  fo)  that  commonly  have  growths  above  1000  per  c.c.,  while 
in  22  (39$)  they  are  never  above  100  per  c.c.  The  Protozoa 
are  somewhat  more  abundant  than  either  the  Chlorophyceae 
or  Cyanophyceae.  Eight  ponds  (12$)  often  have  growths. 


9° 


THE   MICROSCOP  Y   OF  DRINKING-  WA  TER. 


above  lOOO  per  c.c. ;  35  ponds  (60$)  have  growths  between 
100  and  500  per  c.c. 

From  the  table  on  pages  82  and  83  it  also  appears  that 
28  ponds  (49$)  often  have  high  growths  of  one  or  more  of 
these  classes  of  organisms  at  some  time  during  the  year. 
Such  growths,  except  in  the  case  of  certain  diatoms,  are  nearly 
always  noticeable  and  frequently  are  very  troublesome.  In 
17  ponds  the  Diatomaceae  alone  reach  1000  per  c.c.;  in  I 
pond  the  Cyanophycese  alone;  and  in  3  ponds  the  Protozoa 
alone.  One  pond  has  heavy  growths  of  Diatomaceae,  Chloro- 
phyceae  and  Protozoa;  two,  of  Diatomaceae,  Chlorophyceae 
and  Cyanophyceae;  two,  of  Diatomaceae,  Cyanophyceae  and 
Protozoa.  In  two  ponds  all  four  classes  are  found  in  large 
numbers.  There  is  but  one  pond  where  the  organisms  never 
rise  above  100  per  c.c. ;  there  are  16  where  no  class  of  organ- 
isms shows  numbers  greater  than  500  per  c.c. 

For  the  purpose  of  determining  whether  the  depth  of  the 
pond  exercises  any  important  influence  upon  the  growth  of 
the  organisms  the  following  table  was  compiled: 


Depth.* 

Number  per  c.c. 

Number  of  Ponds. 

Diato- 
maceae. 

Chloro- 
phyceae. 

Cyano- 
phyceae. 

Protozoa. 

Deep.   .  . 
Deep  
Deep  
Deep  

Shallow.. 
Shallow.. 
Shallow.. 
Shallow.. 

8 

2 

6 
o 

16 
6 

3 

2 

8 
3 

2 

9 

21 

9 

2 

I 

6 
7 

5 
9 

12 

15 

2 
0 
12 

2 

6 
7 
23 
5 

Usually  between  100  and  500  per  c.c  
Always  below  100  per  c.c  

Occasionally  above  1000  per  c.c  
Usually  between  100  and  500  per  c.c  
Always  beiow  100  per  c.c  

*  Ponds  of  the  Second  Order  are  here  called  "deep  ponds"  ;  ponds  of  the  Third  Order 
"  shallow  ponds  "  ;  no  ponds  of  the  First  Order  are  included.     See  page  63. 

There  are  16  deep  and  41  shallow  ponds.  Of  the  deep 
ponds  63$  at  times  have  growths  of  the  Diatomaceae  above 
1000  per  c.c.,  while  of  the  shallow  ponds  54$  have  such 


GEOGRAPHICAL    DISTRIBUTION   OF    ORGANISMS.          91 

growths.  There  are  no  deep  ponds  where  the  Diatomaceae 
are  lower  than  100  perc.c.,  while  in  15$  of  the  shallow  ponds 
they  are  lower  than  that  figure.  It  thus  appears  that  the 
heavy  growths  of  the  Diatomaceae  are  somewhat  more  likely 
to  be  found  in  the  deep  than  in  the  shallow  ponds.  The 
same  may  be  said  of  the  Chlorophyceae,  though  the  difference 
is  not  so  marked.  31$  of  the  deep  ponds  and  27$  of  the 
shallow  ponds  at  times  have  growths  as  high  as  1000  per  c.c. 
The  Cyanophyceae  and  Protozoa,  on  the  other  hand,  incline 
toward  shallower  water.  In  the  case  of  the  former,  18$  of 
the  deep  ponds  and  34$  of  the  shallow  ponds  at  times  have 
growths  of  1000  per  c.c.,  while  in  the  case  of  the  latter  the 
figures  are  12%  and  32$  respectively 

In  this  connection  it  would  be  of  interest  to  show  statis- 
tically the  relation  that  undoubtedly  exists  between  the 
growths  of  organisms  and  the  character  of  the  material  form- 
ing the  bottoms  of  the  ponds,  but  unfortunately  the  necessary 
data  are  lacking  in  too  many  cases.  So  far  as  observations 
have  been  made,  it  appears  that  muddy  bottoms  are  very 
largely  responsible  for  excessive  growths  of  microscopic 
organisms. 

An  important  question,  and  one  which  is  of  particular 
interest  to  water  analysts,  is  the  relation  between  the  growths 
of  organisms  and  the  chemical  analysis  of  the  water  in  which 
the  organisms  are  found.  Unquestionably  there  is  such  a 
relation,  and  we  should  very  much  like  to  be  able  to  take  up 
a  chemical  analysis  and  say  "this  water  contains  such  and 
such  substances  in  solution,  and,  therefore,  such  and  such 
organisms  may  be  expected  to  thrive  well  in  it."  In  other 
words,  we  desire  to  know  better  the  nature  of  the  necessary 
food-supply  of  the  microscopic  organisms.* 

*  Experiments  upon  this  subject  are  now  in  progress. 


92  THE   MICROSCOP  Y  OF  DRINKING-  WA  TER. 

The  tables  given  on  pages  89  and  90  are  designed  to  show 
in  a  very  general  way  the  relation  between  the  organisms  in 
the  57  selected  ponds  and  some  of  the  important  elements  of 
the  chemical  analysis. 

These  tables  reveal  several  important  facts:  first,  it  is  seen 
that  the  color  of  a  water  has  an  important  influence  upon  the 
number  of  organisms  that  will  be  found  in  it.  Of  the  24 
cases  where  the  Diatomaceae  are  commonly  found  higher  than 
1000  per  c.c.,  12  (or  50$)  occur  in  light-colored  waters,  i.e.,. 
water  having  a  color  lower  than  0.30  on  the  Nessler  scale,  and 
none  occur  in  water  where  the  average  color  is  above  i.oo. 
The  same  fact  is  noticed  in  the  case  of  the  other  organisms, 
but  not  as  markedly  as  with  the  Diatomaceae.  The  reason 
for  this  is,  doubtless,  on  account  of  the  difference  in  specific 
gravity  between  the  diatoms  and  the  other  organisms. 
The  diatoms  are  heavy  by  reason  of  their  siliceous  cell-walls, 
but  the  other  organisms  are  much  lighter  and  some  of  them 
liberate  gas,  causing  them  to  keep  near  the  surface.  The 
depth  to  which  light  penetrates  in  a  body  of  water  makes  less 
difference  with  the  growth  of  the  Cyanophyceae,  for  example. 
than  it  does  with  the  diatoms,  which  constantly  tend  to  sink 
and  which  are  kept  near  the  surface  chiefly  by  the  vertical 
currents  in  the  water. 

The  "excess  of  chlorine"  means  the  difference  between 
the  amount  of  chlorine  found  in  a  sample  of  water  and  that 
found  in  the  unpolluted  water  of  the  same  region.  To  a  cer- 
tain extent  it  represents  the  amount  of  pollution  which  the 
water  has  received.  It  is  important  to  know  whether  this 
element  of  the  analysis  bears  any  relation  to  the  organisms 
and  whether  one  may  rightly  infer  that  a  large  growth  of 
organisms  in  a  reservoir  is  any  indication  of  the  pollution  of 
a  water-supply.  A  study  of  the  tables  shows  that  only  to  a 


GEOGRAPHICAL   DISTRIBUTION  OF  ORGANISMS. 


93 


A. 


Chemical  Analysis 
(pans  per  1,000,000). 

Number  of  Ponds  and  Reservoirs  in  which  the 
Diatomaceac  are 

Often 
above 
looo  per  c.c. 

Occasionally 
above 
looo  per  c.c. 

Usually  be- 
tween too  and 
500  per  c.c. 

Below 
too  per  c.c. 

Color 

o  to    30 

12 

4 

9 

4 

<Nessler  Scale) 

30  to    60 

6 

2 

4 

0 

60  tO  100 

6 

i 

5 

i 

above  100 

o 

i 

i 

i 

Excess  of 

o 

4 

2 

i 

2 

Chlorine 

o.i  to    0.3 

8 

I 

8 

2 

0.4  to    2.5 

8 

3 

10 

2 

above    2.5 

4 

2 

0 

0 

Hardness 

o  to    5. 

2 

I 

3 

3 

.5  to  10. 

7 

4 

5 

2 

i.o  to  20. 

8 

o 

10 

I 

above  20. 

7 

3 

i 

0 

Albuminoid 

o  to  o.ioo 

2 

o 

2 

I 

Ammonia 

o.ioo  to  0.150 

6 

i 

5 

3 

(dissolved) 

o  .  1  50  to  o  .  200 

8 

6 

7 

i 

above  o  200 

8 

i 

5 

i 

Free 

o.ooo  to  o.oio 

3 

2 

5 

3 

Ammonia 

o.oio  to  0.030 

6 

I 

10 

2 

0.030  to  o  loo 

8 

5 

4 

I 

above  o.ioo 

7 

o 

o 

0 

Nitrates 

o  to  0.050 

3 

3 

5 

6 

0.050  to  o.ioo 

ii 

3 

»3 

0 

o.ioo  to  0.200 

6 

2 

i 

o 

above  0.200 

4 

I 

o 

0 

B. 


Number  of  Ponds  and  Reservoirs  in  which  the 
Chlorophyceae  are 


Chemical  Analysis 
(parts  per  1,000,000). 

Often 
above 
looo  per  c.c. 

Occasionally 
above 
1000  per  c.c. 

Usually  be- 
tween loo  and 
500  per  c.c. 

Below 
loo  per  c.c. 

Color 

o  to    30 

2 

5 

M 

8 

(Nessler  Scale) 

30  to    60 

2 

4 

5 

i 

60  to  loo 

i 

2 

8 

2 

above  100 

o 

O 

2 

I 

Excess  of 

o 

J 

3 

4 

I 

Chlorine 

o.  i  to    0.3 

I 

2 

ii 

s 

0.4  to    2.5 

o 

4 

13 

6 

above    2.5 

3 

2 

i 

0 

Hardness 

o    to    5. 

0 

2 

3 

4 

5  .  to  10. 

i 

4 

8 

5 

to.  to  20. 

i 

3 

*3 

2 

above  20. 

3 

2 

5 

I 

Albuminoid 

o  to  o.ioo 

0 

0 

2 

3 

Ammonia 

o.  too  to  o.  150 

0 

4 

7 

4 

(dissolved) 

O.  150  tO  O.2OO 

above  0.200 

2 

3 

5 

2 

12 

8 

3 

2 

Free 

o  to  o.oio 

0 

2 

7 

4 

Ammonia 

o.oio  to  0.030 

0 

I 

*i 

5 

0.030  to  o.  100 

2 

5 

8 

3 

above  o.ioo 

3 

3 

i 

0 

Nitrates 

o  to  0.050 

0 

2 

8 

6 

0.050  to  o.ioo 

2 

6 

»3 

6 

O.IOO  tO  O.2OO 

O 

2 

7 

o 

above  0.200 

3 

1 

i 

o 

94 


THE   MICROSCOPY   OF  DRINKING-WATER. 


c. 


Chemical  Analysis 
(parts  per  1,000,000). 

Number  of  Ponds  ard  Reservoirs  in  which  the 
Cyanophyceae  are 

Often 
above 
looo  per  c.c. 

Occasionally 
above 
TOOO  per  c.c. 

Usually  be- 
tween ioo  and 
500  per  c.c. 

Below 
ioo  per  c.c. 

Color 

o  to    30 

2 

4 

12 

ii 

(Nessler  Scale) 

30  to    60 

2 

3 

4 

3 

60  to  ioo 

3 

2 

i 

7 

above  ioo 

o 

I 

i 

i 

Excess  of 

o 

2 

I 

3 

3 

Chlorine 

o.  i  to    0.3 

I 

3 

5 

IO 

0.410    2.5 

I 

5 

8 

9 

above    2.5 

3 

i 

2 

o 

Hardness 

o    to    5. 

0 

2 

I 

6 

5.  to  TO. 

2 

2 

4 

IO 

10    to  20. 

2 

5 

7 

5 

above  20. 

3 

i 

6 

Albuminoid 

o  to  o.  ioo 

o 

0 

i 

4 

Ammonia 

o.ioo  to  0.150 

o 

3 

6 

6 

(dissolved) 

o.  150  to  0.200 
above  0.200 

2 

5 

5 

2 

8 
.3 

7 

5 

Free 

o  to  o  oio 

0 

2 

i 

to 

Ammonia 

o.oio  to  0.030 

0 

2 

9 

8 

0.030  to  o.  ioo 

3 

5 

6 

4 

above  o.  ioo 

4 

i 

2 

o 

Nitrates 

o  to  0.050 

i 

2 

I 

12 

o  050  to  o.ioo 

3 

4 

IO 

IO 

o.  ioo  to  o  200 

i 

3 

5 

O 

above  0.200 

2 

i 

2 

O 

D. 


Chemical  Analysis 
(parts  per  1,000,000). 

No.  of  Ponds  and  Reservoirs  in  which  the  Protozoa  are 

Often 
above 
looo  per  c.c. 

Occasionally 
above 
looo  per  c.c. 

Usually  be- 
tween ioo  and 
500  per  c.c. 

Below 
ioo  per  c.c. 

Color 

o  to    30 

5 

2 

20 

2 

(Nessler  Scale) 

30  to    60 

i 

3 

6 

2 

60  to  too 

2 

2 

8 

I 

above  ioo 

O 

O 

i 

2 

Excess  of 

O 

I 

2 

5 

t 

Chlorine 

o.  i  to    0.3 

I 

13 

3 

0.4  to    2.5 

2 

3 

15 

3 

above  2.5 

3 

o 

3 

0 

Hardness 

o    to    5. 

o 

o 

7 

3 

5.  to  10. 

3 

0 

12 

2 

10.  to  20. 

6 

10 

2 

above  20. 

4 

i 

6 

0 

Albuminoid 

o  to  o.  ioo 

o 

o 

4 

| 

Ammonia 

o.ioo  to  0.150 

o 

0 

13 

2 

(dissolved) 

o.  150  to  o  200 

5 

2 

12 

3 

above  0.200 

3 

4 

7 

I 

Free 

o  to  o.oio 

! 

i 

9 

2 

Ammonia 

o.oio  to  0.030 

I 

i 

13 

4 

0.030  to  o.  ioo 

2 

5 

IO 

I 

above  o.ioo 

4 

0 

3 

0 

Nitrates 

o  to  o  050 

0 

i 

12 

3 

0.050  to  o.  ioo 

3 

4 

17 

3 

o.ioo  to  0.200 

3 

2 

3 

i 

above  0.200 

2 

0 

3 

0 

GEOGRAPHICAL   DISTRIBUTION    OF  ORGANISMS.          95 

small  extent  does  the  excess  of  chlorine  influence  the  number 
of  organisms  observed,  though  there  is  a  slight  tendency  for 
heavy  growths  of  organisms  to  accompany  high  excess  of 
chlorine.  This  fact  corresponds  with  the  common  observation 
that  vigorous  growths  of  organisms  are  often  observed  in 
ponds  far  removed  from  any  possible  contamination. 

The  hardness  of  a  water,  i.e.,  the  abundance  of  carbonates 
and  sulphates  of  calcium  and  magnesium,  appears  to  have 
some  influence  upon  the  organisms.  This  is  noticed  in  all 
four  classes,  though  it  is  most  marked  in  the  case  of  the 
Diatomaceae  and  Protozoa.  For  example,  of  the  10  ponds 
low  in  hardness  not  one  ever  has  the  Protozoa  as  high  as  1000 
per  c.c.,  while  of  the  1 1  ponds  high  in  hardness  every  one  has 
Protozoa  above  100  per  c.c.,  and  4  commonly  have  them 
above  1000  per  c.c.  It  is  possible  that  it  is  the  greater 
amount  of  free  carbonic  acid  in  the  waters  of  high  hardness 
which  stimulates  the  growth  of  the  organisms  rather  than  the 
salts  of  calcium  and  magnesium. 

The  sanitary  chemical  analysis  ordinarily  states  the  amount 
of  nitrogen  present  in  four  different  forms,  namely,  albumi- 
noid ammonia  (dissolved  and  suspended),  free  an.monia, 
nitrites,  and  nitrates,  which  represent  four  stages  in  the 
change  of  organic  to  inorganic  matter.  Since  nitrogen  is 
essential  to  all  living  matter  we  naturally  expect  that  organ- 
isms will  thrive  best  in  waters  rich  in  that  element.  The 
above  statistics  show  that  this  is  the  case,  and  that  it  is  true 
for  each  class  of  organisms  and  for  the  different  conditions  of 
nitrogen  tabulated.  The  free  ammonia  and  nitrates  appear 
to  be  particularly  influential  in  determining  the  amount  of  life 
present.  For  example,  IO  of  the  13  ponds  low  in  frr.e 
ammonia  never  show  maximum  growths  of  the  Cyanophycea? 


96  THE   MICROSCOPY  OF  DRINKING-WATER. 

above  100  per  c.c.,  while  4  of  the  7  ponds  high  in  free  ammonia 
•commonly  have  growths  above  1000  per  c.c. 

One  must  be  careful  in  these  matters,  however,  not  to 
mistake  cause  for  effect.  Free  ammonia,  for  example,  indi- 
cates organic  matter  in  a  state  of  decay,  and  instead  of  repre- 
senting the  food  of  the  organisms  in  question  it  may  represent 
their  decomposition.  The  interaction  of  the  various  organisms 
is  a  very  complicated  question,  and  the  extent  to  which  one 
organism  lives  upon  the  products  of  decay  of  another  is  not  well 
known. 

Effect  of  Oxygen  and  Free  Carbonic  Acid. — There  is 
reason  to  believe  that  the  amounts  of  dissolved  oxygen  and  free 
carbonic  acid  in  water  exercise  an  important  and  sometimes  a  con- 
trolling influence  on  the  presence  of  microscopic  organisms.  The 
amounts  of  both  of  these  dissolved  gases  vary  greatly  according  to 
different  conditions.  The  controlling  factors  are  usually  tempera- 
ture, the  amount  of  organic  life  in  the  water  and  the  amount  of 
decomposition  which  is  going  on.  Cold  water  will  hold  much 
larger  amounts  of  dissolved  oxygen  in  solution  than  warm  water. 
^Natural  waters  often  lose  their  dissolved  oxygen  through  the 
decomposition  of  organic  matter.  A  good  illustration  of  this 
is  given  on  page  246  in  connection  with  the  phenomena  of  stag- 
nation. 

The  amount  of  dissolved  carbonic  acid  in  natural  waters 
freely  exposed  to  the  air  varies  from  one  or  two  parts  per  million 
to  ten  or  twenty  parts  per  million.  In  large  reservoirs  and 
rapidly  flowing  streams  the  amounts  are  nearer  the  former 
figures,  but  in  swampy  waters  and  in  small  ponds  the  amounts  are 
usually  much  larger.  Decomposition,  while  it  tends  to  decrease 
the  amount  of  dissolved  oxygen,  tends  to  increase  the  amount  of 
•dissolved  carbonic  acid.  When  water  passes  in  a  thin  sheet  over 
&  dam  or  falls  over  stones  in  a  running  brook  it  loses  a  consider- 


GEOGRAPHICAL   DISTRIBUTION  OF  ORGANISMS.        97 

able  amount  of  its  carbonic  acid  and  becomes  at  the  same  time 
well  oxygenated. 

Bodies  of  water  exposed  to  the  air  have  what  may  be  called 
a  respiration.  At  times  they  breath  in  oxygen  and  emit  carbonic 
acid;  at  other  times  they  take  in  carbonic  acid  and  give  out 
oxygen.  There  is  a  continual  adjustment  taking  place  between 
the  gases  present  in  the  water  and  in  the  atmosphere,  and  when 
all  the  facts  which  enter  into  this  transfer  of  oxygen  and  carbonic 
acid  are  known  a  long  step  will  be  taken  towards  solving  the 
problems  of  the  microscopic  organisms.  Some  of  the  micro- 
scopic organisms,  especially  the  chlorophyllaceous  forms,  are 
known  to  be  stimulated  by  the  presence  of  free  carbonic  acid,  and 
in  many  cases  it  is  known  also  that  oxygen  is  necessary.  On  the 
other  hand,  some  of  the  organisms,  such  as  Crenothrix,  are 
thought  to  grow  bevst  when  oxygen  is  absent. 


CHAPTER  VII. 
SEASONAL  DISTRIBUTION  OF  MICROSCOPTC   ORGANISMS. 

THE  microscopic  organisms  found  in  water  show  variations 
in  their  seasonal  occurrence  as  great  and  almost  as  character- 
istic as  do  many  land  plants.  The  succession  of  dandelions, 
buttercups,  and  goldenrod  in  our  fields  finds  its  counterpart 
in  the  succession  of  the  diatoms,  the  green  algae,  and  the  blue- 
green  algae  in  our  lakes  and  ponds.  If  one  examines  the 
water  of  a  lake  continuously  for  a  year  some  interesting 
changes  in  its  flora  and  fauna  may  be  observed.  If  the  lake  is 
a  typical  one  the  water  during  the  winter  will  contain  com- 
paratively few  organisms:  in  the  spring  various  diatoms  will 
appear;  these  will  disappear  in  a  few  weeks  and  in  their 
place  will  come  the  green  algae:  at  the  same  time  the  blue- 
green  algae  may  be  found ;  in  the  fall  both  of  these  will  vanish 
and  the  diatoms  will  develop  again ;  as  the  lake  freezes  these  in 
turn  will  disappear.  Similar  but  less  characteristic  fluctuations 
take  place  among  the  animal  forms.  These  facts  are  shown 
graphically  in  Fig.  15,  which  represents  the  seasonal  changes 
that  occur  among  the  more  important  organisms  in  Lake 
Cochituate.  The  diagram  is  based  on  weekly  observations 
extending  over  a  number  of  years.  The  seasonal  distributions 
of  the  diatoms,  algae,  etc.,  are  so  different  that  it  is  best  to 
consider  each  class  by  itself. 

Diatomaceae. — In  m-  st  natural  ponds  and  storage  reser- 
voirs diatoms  are  far  more  abundant  in  the  spring  and  fall 
than  at  other  seasons.  New  growths  seldom  begin  in  the 

98 


SEASONAL   DISTRIBUTION   OF  ORGANISMS, 


99 


summer  or  winter,  but  the  spring  and  fall  growths  sometimes 
linger  into  the  summer  and  winter  for  a  number  of  weeks. 

o 

The  occurrence  of  diatoms  in  ponds  is  greatly  influenced 
by   the   vertical    circulation   of    the   water.      They    generally 


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FIG.  15. — SEASONAL  DISTRIBUTION   OF   MICROSCOPIC  ORGANISMS  IN  LAKE 

COCHITUATE. 

appear  after  the  periods  of  stagnation  and  during  the  periods 
of  complete  vertical  circulation.  It  has  been  found  that  in 
temperate  lakes  of  the  second  order,  which  have  well-marked 
periods  of  stagnation  in  summer  and  in  winter,  the  spring  and 
fall  growths  of  Asterionella  occur  with  great  regularity  and 
with  about  equal  intensity,  while  in  temperate  lakes  of  the 
third  order,  which  are  stagnant  only  during  the  winter,  the 
Asterionella  growths  in  the  autumn  are  either  small  compared 
with  the  spring  growths  or  are  lacking  altogether.  In  deep 
ponds  the  spring  growths  occur  earlier  and  the  fall  growths 
considerably  later  than  in  shallow  ponds,  thus  again  corre- 
sponding to  the  periods  of  circulation.  In  lakes  of  the  third 
order  diatoms  are  sometimes  found  during  the  summer  after 
periods  of  partial  stagnation. 

Of  the  many  genera  of  diatomacese  that  are  observed  in 
water  only  those   that   are  true  plankton  forms  exhibit  the 


100  THE   MICROSCOPY  OF  DRINKING-WATER. 

spring  and  fall  maxima.  The  most  important  of  these  are 
Asterionella,  Tabellaria,  Melosira,  Synedra,  Stephanodiscus, 
Cyclotella,  and  Diatoma.  Other  genera  are  more  uniformly 
distributed  through  the  year.  All  of  these  seven  genera  are 
sometimes,  but  not  often,  observed  in  the  same  body  of 
water.  As  a  rule  certain  ponds  have  certain  diatoms  peculiar 
to  them.  For  example,  Lake  Cochituate  often  contains  large 
growths  of  Asterionella,  Tabellaria,  and  Melosira;  other 
diatoms  are  to  be  found,  but  they  are  seldom  very  numerous. 
Basin  3  of  the  Boston  Water  Works  contains  Asterionella, 
Tabellaria,  and  Synedra,  but  few  Stephanodiscus  or  Melosira. 
In  Basin  2  only  Synedra  and  Cyclotella  are  found.  In  Basin 
4  Cyclotella  usually  predominates.  Fresh  Pond,  Cambridge, 
Mass.,  is  famous  for  its  Stephanodiscus,  and  Diatoma  is 
common  in  the  water-supply  of  Lynn,  Mass. 

The  genera  that  appear  in  any  pond  are  not  the  same 
every  year.  In  Lake  Cochituate  the  spring  growth  in  1890 
consisted  of  Asterionella  and  Tabellaria;  in  1891  of  Asterio- 
nella with  a  few  Melosira;  in  1892  of  Melosira  chiefly;  in 
1893  of  Melosira  and  Asterionella;  and  in  1894  of  Tabellaria, 
Asterionella,  and  Melosira.  Furthermore,  in  any  season  it  is 
seldom  that  two  genera  attain  their  maximum  development 
at  the  same  time, — sometimes  one  appears  first  and  sometimes 
another.  The  most  interesting  succession  of  genera  that  the 
author  has  observed  occurred  in  1892  in  Chestnut  Hill  Reser- 
voir of  the  Boston  Water  Works.  The  spring  growth  began 
in  April  and  continued  through  July.  For  three  months  the 
total  number  of  diatoms  present  did  not  materially  change, 
but  during  this  time  six  different  genera  appeared  on  the 
scene,  culminated  one  after  another,  and  disappeared.  This 
is  shown  in  Fig.  1 6. 

The  explanation  of  the  peculiar  seasonal  distribution  of 
diatoms  involves  the  answers  to  many  questions.  To  what 


SEA  SON  A  L    DIS  TRIB  U  TION  OF  ORGANISMS:  'J     ' :  *O  \ ' 

extent  are  diatoms  influenced  by  light,  by  temperature,  by 
mechanical  agitation  ?  To  what  extent  are  they  dependent 
upon  oxygen  or  carbonic  acid  dissolved  in  water  ?  What  sort 


APRIL 


MAY 


JULY 


FIG.  16. — SUCCESSION  OF  DIATOMS  IN  CHESTNUT  HILL  RESERVOIR,  1892. 
of  mineral  matter  do  they  require  ?     These  are  questions  not 
yet  fully  answered.     Attempts  have  been  made  to  solve  the 
problems  by  experiment,  but  it  has  been  found  difficult  to 
control  all  the  necessary  conditions  in  the  laboratory. 

The  optimum  temperature  for  the  development  of  the 
diatomaceae  is  not  known  Diatom  growths  have  been 
observed  at  temperatures  ranging  from  35°  to  75°  F.  In 
Lake  Cochituate  the  average  temperature  of  the  water  at  the 
time  of  maximum  Asterionella  growths  is  not  far  from  50°.. 
In  some  lakes  it  is  nearer  60°.  Experimental  evidence  upon 
the  subject  is  weak,  but  there  is  reason  for  believing  that  the 
optimum  temperature  for  the  diatomaceae  is  lower  than  for 
the  green  or  blue-green  algae. 

It  is  known  that  diatoms  are  very  sensitive  to  light.  They 
will  not  grow  in  the  dark  nor  in  bright  sunlight.  Experi- 


THE   MICROSCOP  V   OF  DRINKING-  WA  TER. 


tnents*  made  by  allowing  diatoms  to  grow  in  bottles  at  various 
depths  below  the  surface  have  shown  that  their  growth  is 
nearly  proportional  to  the  intensity  of  the  light.  This  is 


40    60    80  100 


1(00    '  UMEER    FE 


DIAGRAM  SHOWING  THE 
GROWTH  OF  DIATOMS 

AND  THE 

INTENSITY  OF  LIGHT 
AT  VARIOUS  DEPTHS 
LAKE  COCHITUATE   WATER  LOCATED   IN 
LAKE  COCHITUATE   NOV.  29,   1895. 
EXAMINED  DEC.  9,   1895. 
TEMPERATURE  40J44°       COLOR  0.33. 
THE  DIATOMS  WERE  CHIEFLY  ASTERION- 
ELLA  AND  MELOSIRA. 

THE  INTENSITY  OF  LIGHT  AT  DIFFERENT 
DEPTHS  WAS  CALCULATED  ON  THE  ASS- 
UMPTION THAT  A  LAYER  OF  WATER  ONE 
FOOT  IN  DEPTH  ABSORBS  25C/OF  THE 
LIGHT  FALLING  UPON  IT.  ^ 


FIG.  17. 

illustrated  by  Fig.  17.  It  will  be  noticed  that  near  the 
surface, f  where  the  light  was  strong,  they  multiplied  rapidly, 
but  below  the  surface  the  rate  of  multiplication  was  much 
slower,  and  at  a  certain  depth  no  multiplication  took  place. 
This  depth-limit  of  growth  varied  according  to  the  color  and 
transparency  of  the  water,  being  greatest  in  the  water  having 
the  least  color.  In  one  reservoir,  where  the  color  was  86, 
the  limit  of  growth  was  8  ft. ;  in  another,  where  the  color 
was  60,  it  was  12  ft.;  and  in  another,  with  a  color  of  29,  it 
was  15  ft.  No  observations  were  made  in  colorless  waters, 
but  in  them  the  limit  of  growth  is  as  great  as  25  or  50  ft.,  and 
perhaps  even  much  more  than  this. 

The  specific  gravity  of  diatoms  plays  an  important  part  in 
their  seasonal  distribution.  In  absolutely  quiet  water  most 
.diatoms  sink  to  the  bottom,  but  very  slight  vertical  currents 

*  By  the  author. 

fThe  growth  at  the  depth  of  6  inches   was    greater    than  at   the  im- 
mediate surface,  where  the  direct  sunlight  was  too  strong. 


SEASONAL   DISTRIBUTION  OF  ORGANISMS  103 

are  sufficient  to  prevent  them  from  sinking.  A  few  forms 
appear  to  have  a  slight  power  of  buoyancy,  and  some  genera 
are  somewhat  motile. 

Diatoms  are  said  to  be  positively  heliotropic,  that  is,  they 
tend  to  move  towards  the  light.  In  some  of  the  motile  forms 
this  power  is  quite  strong.  In  most  of  the  plankton  genera 
this  power  is  weak.  They  will  not  move  upwards  towards 
the  light  through  any  great  depth  of  water.  It  is  possible, 
however,  that  the  power  of  heliotropism  varies  with  the 
intensity  of  the  light,  but  experimental  evidence  on  this  point 
is  lacking. 

Diatoms  require  air  for  their  best  development.  Experi- 
ment has  shown  that  they  will  not  multiply  in  a  jar  where  a 
thin  layer  of  oil  covers  the  surface  of  the  water :  that  in  cul- 
tures in  jars  of  various  shapes,  the  one  that  has  the  least 
depth  of  water  and  the  greatest  amount  of  surface  exposed  to 
the  air  will  show  the  greatest  multiplication;  that  in  bottles 
exposed  at  the  same  depth  beneath  the  surface  of  a  reservoir, 
one  with  bolting-cloth  tied  over  the  mouth  will  show  a 
greater  development  of  diatoms  than 'one  tightly  stoppered. 

The  nature  of  the  food-material  of  diatoms  is  not  well 
known.  Observations  seem  to  show  that  they  require  nitro- 
gen iii  the  form  of  nitrates  or  free  ammonia  (perhaps  both), 
silica,  and  more  or  less  mineral  matter,  such  as  the  salts  of 
magnesium,  calcium,  iron,  manganese,  etc.,  but  the  amounts 
of  these  various  substances  required  has  not  been  determined. 

These  facts  enable  one  to  formulate  a  theory  for  the 
explanation  of  the  occurrence  of  maximum  growths  of  diatoms 
after  the  periods  of  stagnation  and  during  the  periods  of  cir- 
culation. 

During  the  periods  of  stagnation  the  lower  stratum  of  water 
in  a  deep  lake  undergoes  certain  changes  that  are  very  pro- 


104  THE   MICROSCOPY   OF  DRINKING-WATER. 

nounced  if  the  bottom  of  the  lake  holds  any  accumulation  of 
organic  matter.  The  organic  matter  decays,  the  oxygen  be- 
comes exhausted,  decomposition  proceeds  under  the  action  of 
the  anaerobic  bacteria,  the  free  ammonia  increases,  and  other 
organic  and  inorganic  substances  become  dissolved  in  the 
water.  During  the  period  of  circulation  this  foul  water 
reaches  the  surface,  further  oxidation  takes  place,  and  com- 
pounds favorable  to  the  growth  of  diatoms  are  formed.  At 
the  same  time  the  vertical  currents  carry  to  the  surface  the 
diatoms,  or  their  spores,  that  have  been  lying  dormant  at  the 
bottom,  where  they  could  not  grow  because  of  darkness  or 
because  of  the  absence  of  proper  food  conditions.  Carried 
thus  towards  the  surface,  where  there  is  an  abundance  of 
light,  air,  and  nutrition,  they  multiply  rapidly.  The  extent 
of  their  development  depends  upon  the  amount  of  food- 
material  present,  the  temperature  of  the  water,  and  the 
amount  of  vertical  circulation.  If  the  upper  layers  become 
stratified  and  the  surface  remains  calm  for  a  number  of  days 
the  diatoms  will  settle  in  the  water  into  a  region  where  the 
light  is  less  intense.  If  they  sink  far  enough  they  enter  a 
region  where  the  light  is  not  sufficient  for  their  growth,  and 
if  they  sink  below  the  thermocline  succeeding  vertical  circu- 
lation of  the  upper  strata  will  not  affect  them.  Unable  to 
reach  the  surface  by  their  own  power  they  will  sink  to  the 
bottom  and  remain  through  another  period  of  stagnation. 

In  small  reservoirs  that  are  constantly  supplied  with  water 
rich  in  diatom  food  and  that  are  so  shallow  that  even  at  the 
bottom  the  light  is  strong  enough  for  their  development,  the 
seasonal  distribution  follows  somewhat  different  laws.  This  is 
the  case  in  many  open  reservoirs  where  ground-water  is  stored. 

Chlorophyceae. — The  Chlorophyceae  are  most  abundant 
in  water-supplies  during  the  summer.  They  are  seldom 


SEASONAL   DISTRIBUTION  OF  ORGANISMS.  10$ 

found  in  winter.  The  curve  showing  their  development 
is  more  nearly  parallel  with  the  curve  showing  the  tem- 
perature of  the  water  than  is  that  of  any  other  class  of 
organisms.  The  maximum  growth  is  usually  in  July  or 
August,  though  some  genera  culminate  as  early  as  June  and 
others  as  late  as  September  or  even  October.  The  late 
growths  are  usually  associated  with  the  phenomenon  of  stag- 
nation. 

The  optimum  temperature  for  the  different  genera  is  not 
known.  It  seems  probable  that  any  of  the  common  forms 
are  able  to  grow  vigorously  between  60°  and  80°  F.  if  their 
food-supply  is  favorable.  It  is  possible  for  some  of  the  green; 
algae  to  become  acclimated  to  considerable  extremes  of  heat 
or  cold.  Protococcus  nivalis  is  found  in  the  arctic  regions, 
and  Conferva  has  been  observed  in  water  at  a  temperature  of 
115°  F. 

Cyanophyceae. — The  seasonal  distribution  of  the  Cyano- 
phyceae  is  similar  to  that  of  the  Chlorophyceae,  but  as  a  rule 
the  maximum  growths  occur  a  little  later  in  the  season.  The 
Cyanophyceae  seem  to  be  attuned  to  a  slightly  higher  tempera- 
ture than  the  Chlorophyceae.  They  often  show  a  great 
increase  after  a  period  of  hot  weather.  Anabaena,  Clath- 
rocystis,  and  Coelosphaerium  seldom  give  trouble  unless  the 
temperature  of  the  water  is  above  70°  F.  Aphanizomenon 
is  more  independent  of  temperature.  It  apparently  prefers 
a  lower  temperature  than  most  of  the  Cyanophyceae.  In 
some  ponds  it  is  present  throughout  the  entire  year,  even 
when  the  surface  is  frozen.  On  one  occasion  it  grew  under 
the  ice  in  Laurel  Lake,  Fitzwilliam,  N.  H.,  and  became 
frozen  into  the  ice  to  such  an  extent  that  the  ice-cutters  were 
alarmed  at  the  green  color.  In  Lake  Cochituate,  Aphani- 
zomenon reaches  its  greatest  growth  in  the  autumn.  This 
accounts  for  the  maximum  of  the  curve  of  Cyanophyceae; 


IO6  THE   MICROSCOPY  OF  DRINKING-WATER. 

in  Fig.  15  occurring  in  October  instead  of  in  August  or  Sep- 
tember. 

Schizomycetes  and  Fungi. — These  forms  have  no  well- 
marked  periods  of  seasonal  distribution.  They  are  liable 
to  be  found  at  any  season.  Mold  hyphae  are  frequently 
found  at  the  bottom  of  lakes  during  the  summer,  and  at 
the  surface  under  the  ice  in  winter.  Crenothrix  may  be 
found  in  the  stagnant  water  at  the  bottom  of  a  deep  lake 
during  the  summer,  and  at  all  depths  in  the  autumn  after  the 
overturning  of  the  lower  layers  of  water.  Crenothrix  has 
been  observed  during  the  summer  in  swamps  in  company 
with  Anabaena  and  other  Cyanophyceae. 

Protozoa.  -The  seasonal  distribution  of  the  Protozoa, 
taken  as  an  entire  group,  is  extremely  variable  and  differs 
considerably  in  different  ponds.  No  curve  can  be  drawn  that 
will  represent  all  cases.  In  Lake  Cochiluate  the  curve  has  a 
major  maximum  in  the  spring,  a  minor  maximum  in  the 
autumn,  with  the  summer  minimum  lower  than  that  in  the 
winter.  In  Mystic  Lake  the  curve  has  but  one  maximum, — 
in  the  summer.  These  differences  are  due  to  the  fact  that 
the  group  of  Protozoa  is  a  broad  one,  and  includes  organisms 
that  differ  widely  in  their  mode  of  life. 

The  Rhizopoda  are  found  at  all  seasons  of  the  year,  but 
they  are  most  numerous  in  the  autumn  after  the  period  of  sum- 
mer stagnation.  These  organisms  live  upon  the  ooze  on  the 
bottom  and  sides  of  ponds  and  upon  twigs  and  aquatic  plants. 
There  they  are  found  most  abundantly  in  the  summer.  The 
vertical  currents  of  the  autumnal  circulation  scatter  them 
through  the  water  and  cause  the  maximum  number  of  float- 
ing forms  to  be  observed  during  October  and  November. 
There  is  a  minor  maximum  during  the  period  of  spring  cir- 
culation. Some  plankton  forms,  such  as  Actinophrys,  are 
most  abundant  in  summer. 


SEASONAL   DISTRIBUTION   OF  ORGANISMS.  IO/ 

Of  the  Flagellata,  Euglena,  Raphidomonas  and  Phacus 
are  most  abundant  from  June  to  September:  Trachelomonas 
is  found  at  all  seasons,  but  is  most  common  in  the  fall  after 
•the  period  of  summer  stagnation:  Mallomonas  is  found  from 
April  to  October,  but  is  usually  most  abundant  in  the  autumn : 
Cryptomonas  occurs  in  some  ponds  only  in  the  late  fall  and 
winter:  Synura  and  Dinobryon  are  generally  most  numerous 
in  the  spring  and  autumn,  but  heavy  growths  have  been  ob- 
served at  all  seasons:  Uroglena  seems  to  prefer  cold  weather, 
but  vigorous  growths  have  been  noted  in  June. 

The  Dino-flagellata,  Glenodinium  and  Peridinium,  are 
usually  most  abundant  during  warm  weather,  but  they  are 
liable  to  occur  at  any  season.  Ceratium  seldom  appears 
before  July,  and  it  usually  disappears  before  cold  weather. 

Of  the  Infusoria,  most  of  the  ciliated  forms  prefer  warm 
water:  Codonella  and  Tintinnus  occur  after  periods  of  stag- 
nation: Vorticella  and  Epistylis  are  distinctly  summer  organ- 
isms: and  Bursaria  and  Stentor  are  also  found  in  summer. 
Acinteta  is  most  abundant  during  warm  weather. 
The  Protozoa  that  attain  their  greatest  development  in 
summer  are  those  forms  that  are  closely  allied  to  the  vegetable 
kingdom  ;  namely,  the  Dino-flagellata  and  some  of  the  Flagel- 
lata that  are  rich  in  chlorophyll.  A  few  genera  that  occur  most 
.abundantly  in  the  spring  and  fall  have  a  brownish-green  color 
like  that  of  the  diatoms,  which  also  have  spring  and  fall  max- 
ima. The  Ciliata  that  live  upon  decaying  organic  matter  are 
attuned  to  a  comparatively  high  temperature, — about  75°  F. 
This  has  been  demonstrated  by  experiment,  and  it  corresponds 
with  the  time  of  their  observed  maximum.  Those  Protozoa 
that  exhibit  a  strictly  animal  mode  of  nutrition  are  most  abun- 
dant at  those  seasons  when  there  is  plenty  of  food-material  in 
the  shape  of  minute  organisms  or  finely  divided  particles  of 
•organic  matter.  This  partially  explains  why  growths  are 


IO8  THE  MICROSCOPY   OF  DRINKING-WATER. 

sometimes  present  in  the  winter  when  bacteria  are  numerous, 
or  after  periods  of  stagnation  when  particles  of  organic  matter 
from  the  bottom  have  been  scattered  through  the  water. 

Rotifera. — Rotifera  are  found  at  all  seasons  of  the  year, 
but  are  most  numerous  between  June  and  November.  In 
many  ponds  the  maximum  occurs  in  the  autumn.  Some 
genera  are  perennial,  others  are  periodic  in  their  occurrence. 
Anuraea  and  Polyarthra  are  found  throughout  the  year,  but 
their  numbers  rise  and  fall  at  intervals  corresponding  to  the 
hatching  season.  Conochilus  is  often  abundant  in  June, 
Asplanchna  in  July  and  August,  and  Synchaeta  in  August  and 
September.  The  littoral  Rotifera  are  most  abundant  during 
the  summer. 

The  Rotifera  feed  upon  the  smaller  microscopic  organisms, 
and  their  seasonal  distribution  is  largely  influenced  by  the 
amount  of  this  food-supply.  The  reactions  of  the  Rotifera 
to  light,  temperature,  etc.,  are  not  well  known. 

Crustacea.* — The  number  of  Crustacea  present  at  differ- 
ent seasons  varies  greatly  in  different  bodies  of  water.  It  is 
influenced  largely  by  the  genera  that  are  present.  Different 
genera  vary  considerably  in  their  seasonal  distribution.  Some 
are  found  at  all  seasons,  while  others  occur  only  at  certain 
times.  The  perennial  forms  may  have  several  maxima  dur- 
ing the  year,  corresponding  to  the  hatching  of  different 
broods.  As  a  rule  Crustacea  are  most  numerous  in  the 
spring,  but  minor  maxima  may  occur  during  the  summer  and 
autumn  and  rarely  in  the  winter. 

Temperature,  food-supply,  and  competition  are  said  to  be 
the  chief  factors  that  influence  the  seasonal  distribution  of 
the  Crustacea. 

*  Fora  full  discussion  of  the  seasonal  distribution  of  the  Crustacea  the 
reader  is  referred  to  Dr.  Birge's  studies  of  the  Crustacea  of  Lake  Mendota. 


CHAPTER  VIII. 

HORIZONTAL  AND  VERTICAL  DISTRIBUTION  OF   MICRO- 
SCOPIC  ORGANISMS. 

THE  plants  and  animals  that  inhabit  lakes  and  ponds  may 
be  classified  according  to  their  habitat,  but  it  is  sufficient 
here  to  consider  them  either  as  littoral  or  limnetic. 

The  littoral  organisms  may  be  said  to  include  all  those 
forms  that  are  attached  to  the  shore  or  to  plants  growing  on  the 
shore,  besides  a  host  of  others  which,  though  free-swimming, 
are  almost  invariably  associated  with  the  attached  forms. 

The  limnetic  or  pelagic  organisms  are  those  that  make 
their  home  in  the  open  water.  They  float  or  swim  freely  and 
are  drifted  about  by  every  current.  Collectively  they  make 
up  the  greater  part  of  the  plankton.  They  include  almost 
all  the  troublesome  odor-producing  organisms  in  water-sup- 
plies. In  the  open  water,  however,  one  often  finds  some  of 
the  littoral  forms  that  have  been  detached  from  the  shore  and 
scattered  through  the  water  by  the  currents,  or  that  are  para- 
sitically  attached  to  some  of  the  limnetic  forms.  Then  there 
are  organisms  that  may  be  said  to  be  facultative  limnetic 
forms,  that  is,  they  are  sedentary  or  free-swimming  at  will. 
The  true  limnetic  forms,  however,  are  the  most  important  in 
Avater-supplies,  and  their  horizontal  and  vertical  distributions 
are  now  to  be  considered. 

IOQ 


I  10  THE   MICROSCOPY  OF  DRINKING-WATER. 

Horizontal  Distribution. — The  horizontal  distribution  of 
the  limnetic  organisms  is  usually  quite  uniform  within  any 
limited  area,  but  through  the  entire  body  of  a  lake  the  num- 
ber of  organisms  may  show  considerable  variation.  This  is 
quite  noticeable  in  long,  narrow  reservoirs  that  have  streams 
entering  at  one  end  and  discharging  at  the  other.  In  such 
reservoirs  the  organisms  are  generally  most  numerous  at  the 
lower  end.  If,  however,  the  water  in  the  influx  stream  con- 
tains many  organisms  the  numbers  may  be  higher  at  the 
upper  end,  diminishing  gradually  as  the  water  of  the  stream 
becomes  mixed  with  that  of  the  reservoir.  Sometimes  the 
mixing  takes  place  slowly  and  the  influent  water  passes  as  a 
current  far  into  the  reservoir.  This  tends  to  distribute  the 
organisms  in  streaks.  In  lakes  with  uneven  margins  the 
horizontal  distribution  may  vary  greatly,  and  the  number  of 
organisms  found  in  coves  may  be  quite  different  from  the  num- 
ber found  in  the  open  water.  The  horizontal  distribution  of 
diatoms  is  influenced  to  some  extent  by  the  depth  of  the  lake. 
There  is  in  Massachusetts  a  lake  covering  about  250  acres. 
Near  one  side  of  it  there  is  a  deep  hole,  that  has  an  area  of 
about  five  acres,  where  the  stagnation-phenomena  are  very 
pronounced.  When  the  growths  of  diatoms  occur  in  the 
spring  and  fall  the  numbers  are  very  much  higher  in  the 
vicinity  of  this  deep  hole  than  elsewhere  in  the  lake. 

Areas  of  shallow  flowage  exert  a  marked  effect  on  the  hori- 
zontal distribution  of  the  microscopic  organisms. 

The  wind  also  has  a  great  influence,  and  in  many  bodies 
of  water  it  is  the  controlling  influence.  The  organisms,  par- 
ticularly the  Cyanophyceae,  are  driven  in  the  direction  of  the 
wind  and  accumulate  towards  the  lee  shore.  It  is  possible 
that  horizontal  thermal  convection  currents  may  influence  the 
distribution  to  some  extent. 


VER  TIC  A  L    D  IS  TRIE  U  TION  OF  ORGA  NISMS.  I  I  I 

Vertical  Distribution. — The  laws  that  govern  the  vertical 
distribution  of  the  microscopic  organisms  are  more  compli- 
cated than  those  which  govern  their  horizontal  distribution. 
The  latter  affect  the  organisms  mechanically;  the  former, 
vitally.  While  their  specific  gravity  and  the  vertical  currents 
produced  mechanically  or  thermally  play  an  important  part, 
the  amount  of  food-material  and  dissolved  oxygen  and  the 
amount  of  heat  and  light  influence  the  very  life  of  the  organ- 
isms. 

In  a  lake  of  the  second  order  the  determining  factors  vary 
at  different  depths  and  at  different  seasons.  In  the  summer, 
for  example,  the  conditions  above  the  thermocline  *  are  very 
different  from  those  below  it.  Near  the  surface  the  water  is 
warm,  the  light  is  strong,  oxygen  is  very  abundant,  and  there 
are  vertical  currents.  Near  the  bottom  the  water  is  cold,  the 
light  is  weak,  the  oxygen  may  be  exhausted,  and  the  water 
is  perfectly  quiet.  With  these  conditions  chlorophyll-bearing 
organisms  naturally  thrive  best  above  the  thermocline.  They 
seldom  develop  below  it. 

It  has  been  shown  by  experiment  that  the  development 
of  diatoms  is  greatest  near  the  surface  and  that  it  decreases 
downwards  as  the  light  decreases.  In  nature,  however,  it 
cannot  be  expected  that  the  number  of  diatoms  in  the  differ- 
ent layers  of  water  will  follow  this  law  closely,  because  the 
diatoms  are  heavy  and  constantly  tend  to  sink  and  because 
the  water  above  the  thermocline  is  more  or  less  stirred  up. 
One  would  expect  rather  to  find  a  uniform  vertical  distribution 
above  the  thermocline,  and  below  it  a  rapid  decrease  in  the 
number  of  organisms.  Such  a  distribution  is  common.  The 
following  instances  of  the  vertical  distribution  of  Asterionella 
and  Tabellaria  in  Lake  Cochituate  may  be  cited  in  illustra- 

*  See  page  64. 


I  1 2  THE   MICROSCOP  Y  OF  DRINKING-  WA  TER 

tion:  in  both  instances  the  thermocline  was  located  between 
.20  and  30  ft. 

VERTICAL   DISTRIBUTION    OF   ASTERIONELLA    AND 
TABELLARIA    IN    LAKE   COCHITUATE. 

NUMBERS    PER    C.C. 


Depth 
in  Feet. 

Asterionella. 
May  7,  1891. 

Tabellaria. 
May  24,  1890. 

Surface 

3752 

1886 

10  ft. 

3736 

1448 

20    " 

3716 

1396 

25  " 



484 

30  " 

1784 

298 

40  " 

456 



50  " 

536 



60  " 

I78 

96 

This  manner  of  distribution  is  most  common  during  pe- 
riods of  rapid  development,  when  a  gentle  breeze  is  stirring. 
In  very  quiet  weather  and  during  periods  of  declining  growth 
diatoms  sink  rapidly,  and  at  such  times  they  may  be  found 
most  numerous  at  the  thermocline  or  at  the  bottom.  During 
periods  of  complete  vertical  circulation  the  vertical  distribu- 
tion may  be  quite  uniform  from  top  to  bottom.  The  diatoms 
found  at  the  bottom  of  a  deep  lake  are  usually  less  vigorous 
than  those  near  the  surface. 

The  Chlorophyceae  and  Cyanophyceae  are  much  lighter  in 
weight  than  the  diatoms,  and  some  of  them  contain  oil- 
globules  and  bubbles  of  gas.  The  forces  tending  to  keep 
them  near  the  surface  are  greater  therefore  than  in  the  case 
of  the  diatoms.  These  forms  are  seldom  found  below  the 
thermocline,  and  even  above  the  thermocline  they  show  con- 
siderable variations  at  different  depths.  The  Cyanophyceae 
especially  collect  near  the  surface.  In  quiet  waters  they 
often  form  unsightly  and  ill-smelling  scums.  Occasional 
-exceptions  to  the  general  rule  are  observed.  Microcystis,  for 


VER  TICA  L    D  IS  TRIE  U  TION   OF  ORGA  NISMS.  I  I  3 

•example,  is  usually  more  abundant  in  Lake  Cochituate  just 
below  the  thermocline  than  it  is  at  the  surface.  On  July  31, 
1895,  the  numbers  of  standard  units  of  Microcystis  at  dif- 
ferent depths  were  as  follows:  Surface,  94;  30  ft.,  342;  60 
ft.,  140. 

It  is  interesting  to  notice  that  a  sudden  wind  affects  the 
vertical  distribution  of  the  Cyanophyceae  and  the  Diatomaceae 
in  opposite  ways.  It  tends  to  decrease  the  number  of  blue- 
green  algae  at  the  surface  by  preventing  the  formation  of 
scums,  while  it  increases  the  number  of  diatoms  by  prevent- 
ing them  from  sinking. 

The  Protozoa,  as  a  class,  seek  the  upper  strata  of  water. 
Euglena  sometimes  form  a  scum  upon  the  surface.  Uroglena, 
Synura,  etc.,  are  often  most  numerous  in  winter  just  beneath 
the  ice.  The  Dino-flagellata  are  distinctly  surface  forms. 
-Some  of  the  Protozoa  seem  to  avoid  direct  sunlight  and  keep 
away  from  the  upper  surface  of  the  water,  though  they  may 
be  very  abundant  at  a  depth  of  one  or  two  feet.  The  Ciliata 
and  those  Protozoa  that  have  a  distinctly  animal  mode  of 
nutrition  are  more  irregularly  distributed  through  the  vertical. 
The  Rhizopoda  are  most  abundant  near  the  bottom. 

At  times  some  of  the  Protozoa  are  more  numerous  at  the 
thermocline  than  elsewhere  in  the  vertical.  An  interesting 
illustration  of  this  occurred  in  Lake  Cochituate  in  the  summer 
of  1896.  Mallomonas  are  not  ordinarily  abundant  in  this  lake, 
but  on  June  24  they  suddenly  appeared  just  below  the 
thermocline.  At  the  mid-depth  (30  ft.)  there  were  116  per 
•c.c.,  at  the  bottom  there  were  42  per  c.c.,  but  at  the  surface 
there  were  none.  They  developed  rapidly,  and  on  August  4 
there  were  3640  at  the  mid-depth.  The  growth  continued 
until  September,  and  during  this  time  the  largest  number 
observed  at  the  bottom  was  276  per  c.c.,  while  above  the 


114  THE    MICROSCOPY   OF  DRINKING-WATER. 

thermocline  scarcely   an   individual   was  found.      On  July  17 
the  vertical  distribution  was  as  follows: 


VERTICAL    DISTRIBUTION    OF    MALLOMONAS    IN    LAKE 
COCHITUATE,  JULY  17,  1896. 

Depth.  Number  per  c.c.        Temperature  Fahr. 

Surface  o  77-3° 

10  ft.  o  75.2 

15   "  2  62.0 

20  ft.  1454  47-7 

25  "  794  43-7 

30  "  548  43.2 

40  "  112  42.5 

50  "  88  41.4 

60  "  64  40.8 

Synura  and  other  Protozoa  have  sometimes  shown  a 
similar  vertical  distribution.  Whether  this  concentration 
at  the  thermocline  is  due  to  food-material,  to  light,  or  to 
temperature  is  not  definitely  known.  Mallomonas  are  motile 
and  are  known  to  be  positively  heliotropic.  In  the  winter 
they  are  often  numerous  under  the  ice.  It  is  possible  that 
they  have  a  low  temperature  attunement,  and  that  in  the 
instance  above  cited  they  collected  as  near  the  surface  as 
their  temperature  attunement  would  permit.  This  would 
accord  with  the  fact  that  they  are  most  numerous  in  the 
spring  and  fall. 

Rotifera  and  Crustacea  are  most  numerous  above  the  ther- 
mocline, and  as  a  rule  they  are  concentrated  in  the  upper  strata 
of  water.  During  the  winter  they  are  sometimes  abundant 
at  the  bottom.  Different  genera  react  differently  to  light, 
heat,  etc.,  and  therefore  the  vertical  distribution  of  these 
organisms  is  somewhat  complicated.  Some  of  them  show  a 
slight  daily  migration  towards  the  surface  at  night,  and  away 
from  the  surface  in  the  daytime. 


VERTICAL   DISTRIBUTION   OF  ORGANISMS. 


I  J 


The  Schizomycetes  are  usually  more  abundant  at  the 
bottom  of  a  pond  than  at  the  surface.  Mold  hyphae  are  often 
numerous  in  winter  just  under  the  surface  of  the  ice. 

In  spite  of  the  tendencies  of  the  organisms  to  choose 
their  favorite  habitat  in  a  body  of  water,  the  mechanical  effects 
of  winds,  currents,  gravity,  etc.,  are  so  great  that  in  most 
ponds  and  reservoirs  used  for  water-supply  (except  very  deep 
ones)  the  average  number  of  organisms  of  all  kinds  through 
the  year  does  not  vary  much  at  different  depths.  This  is 
illustrated  by  the  following  table : 

TABLE  SHOWING  THE  RELATIVE  NUMBER*  OF  MICROSCOPIC 
ORGANISMS  OF  ALL  KINDS  AT  THE  SURFACE,  MID-DEPTHr 
AND  BOTTOM  OF  THE  RESERVOIRS  OF  THE  BOSTON 
WATER  WORKS. 


Locality. 

Depth. 

1890. 

1891. 

1892. 

1893. 

i£94. 

1895. 

1896. 

Surface 

454 

736 

523 

389 

416 

355 

507 

Lake  Cochituate 

30  ft. 

304 

569 

528 

336 

365 

373 

6f57 

60  ft. 

357 

650 

626 

316 

309 

353 

544 

Surface 

68 

322 

268 

116 

45 

61 

87 

Basin  2 

13  ft. 

80 

273 

256 

98 

49 

56 

120 

25ft. 

64 

268 

229 

98 

33 

47 

78 

Surface 

152 

277 

5M 

38i 

289 

621 

524 

Basin  3 

15  ft. 

182 

267 

523 

303 

194 

543 

467 

30  ft. 

131 

323 

481 

3" 

179 

485 

498 

Surface 

50 

129 

269 

112 

28 

57 

94 

Basin  4 

20  ft. 

38 

95 

268 

84 

20 

35 

108 

40  ft. 

25 

83 

235 

66 

20 

25 

1  06 

Surface 

87 

105 

189 

Basin  6 

2*  ft. 

52 

58 

118 

50  ft. 

72 

53 

104 

*  For  the  years  1890  to  1893  the  results  were  givtn  in  "  Number  ot  Organisms  per  c.c." 
Since  Jan.  i,  1893,  the  results  have  been  given  in  Number  of  Standard  Units  per  c.c.  (One 
standard  unit  equals  400  square  microns.) 

The  vertical  distribution  varies  at  different  seasons,  as  the 

following  table  illustrates: 


n6 


THE   MICROSCOPY  OF  DRINKING-WATER. 


TABLE  SHOWING  THE  RELATIVE  NUMBER  OF  ORGANISMS 
(STANDARD  UNITS)  PER  C.C.  AT  THE  SURFACE,  MID- 
DEPTH,  AND  BOTTOM  OF  THE  RESERVOIRS  OF  THE 
BOSTON  WATER  WORKS  DURING  1895. 


Locality. 

Depth. 

>, 

u 
C 

rt 

3 

.C 

rt 

o. 

c 

_^ 

So 
3 

ptember. 

1 

ovember. 

1-' 

S 
u 

g 

§ 

fc 

3 

s 

i  —  , 

</) 

0 

* 

Q 

Lake  Cochituate 

Surface 
3o  ft. 

255 
407 

34 

21 

IO 

23 

97 
tog 

1  88 
149 

437 
188 

480 

539 

329 

«37 

450 
400 

"59 
"99 

762 

Q2I 

355 

60  ft. 

422 

232 

55 

IOI 

133 

z88 

503 

290 

53 

252 

1198 

808 

353 

Surface 

6 

8 

6 

49 

56 

IOQ 

163 

152 

82 

72 

IS 

18 

61 

Basin  2 

13  ft. 

6 

7 

18 

25 

59 

76 

1  95 

108 

93 

53 

'7 

56 

25  ft. 

4 

7 

17 

22 

47 

<>3 

1  60 

88 

74 

49 

22 

9 

47 

Surface 

n 

3 

14 

62 

37S 

787 

"97 

i67s 

1778 

1227 

266 

53 

621 

Basin  3 

15  ft. 
30  ft. 

18 
47 

i 
4 

13 

46 

57 

260 
235 

768 
597 

1072 
633 

1146 

1813 
1487 

1161 
1342 

253 
222 

34 
37 

543 

485 

Basin  4 

Surface 

20  ft. 

78 

18 

74 
19 

IO 

27 

79 
37 

76 
47 

123 
43 

75 
78 

30 

2Q 

45 

ss 

40 

37 

22 

57 

40  ft. 

13 

18 

12 

21 

48 

38 

33 

21 

26 

25 

Surface 

4I 

5° 

36 

64 

91 

193 

20.3 

9i 

243 

186 

41 

»3 

105 

Basin  6 

25  ft. 

28 

10 

4 

57 

42 

61 

46 

65 

iqo 

S6 

9 

58 

50  ft. 

4 

5 

21 

76 

51 

39 

18 

47 

«3 

214 

60 

16 

53 

A  further  analysis  of  the  results  at  Lake  Cochituate  shows 
the  vertical  distribution  of  the  different  classes  of  organisms 
to  be  as  follows: 

RELATIVE  NUMBER  OF  ORGANISMS  (STANDARD  UNITS)  PER 
C.C.  AT  THE  SURFACE  AND  BOTTOM  OF  LAKE  COCHIT- 
UATE. 

AVERAGE    FOR    THE    YEAR    1895. 


Diato- 

maceae. 

Chloro- 
phyceae. 

Cyano- 
phyceae. 

Protozoa. 

Rotifera. 

Miscella- 
neous. 

.  Total. 

Surface  
Bottom  

144 

160* 

79 
16 

108 
67 

i  J7 

i   10 

3 
I 

99  1 

355 
353 

*  If  the  dead  and  empty  cells  were  excluded  this  figure  would  be  much  lower, 
t  Chiefly  Crcnothrix. 


CHAPTER   IX. 
ODORS   IN   WATER-SUPPLIES. 

THE  senses  of  taste  and  odor  are  distinct,  but  they  are 
closely  related  to  each  other.  There  are  some  substances, 
like  salt,  that  have  a  taste  but  no  odor,  and  there  are  other 
substances,  like  vanilla,  that  have  a  strong  odor  but  no  taste. 
It  is  believed  that  the  sense  of  taste  is  quite  limited  and  that 
many  so-called  tastes  are  really  odors,  the  gas  or  vapor  given 
off  by  the  substance  tasted  reaching  the  nose  not  only  through 
the  nostrils  but  through  the  posterior  nares.  Thus  an  odor 
tasted  is  often  stronger  than  an  odor  smelled. 

Chemically  pure  water  is  free  from  both  taste  and  odor. 
Water  containing  certain  substances  in  solution,  as  sugar, 
salt,  etc.,  may  have  a  decided  taste  but  no  odor.  Such 
taste-producing  substances  are  met  with  in  mineral  waters  or 
in  brackish  or  chalybeate  waters,  but  as  a  rule  they  are  not 
offensive  and  they  seldom  affect  large  bodies  of  water.  Most 
of  the  bad  tastes  observed  in  drinking-water  are  due  not  to  in- 
organic but  to  organic  substances  either  in  solution  or  in  sus- 
pension. Such  substances  almost  invariably  produce  odors 
as  well  as  tastes.  The  subject  may  be  pursued  therefore 
from  the  standpoint  of  odor,  though  in  many  instances  the 
best  way  to  observe  the  odor  of  the  water  is  to  taste  it. 

Water  taken  directly  from  the  ground  and  used  immedi- 
ately is  usually  odorless.  In  certain  sections  of  the  country  it 
has  a  sulphurous  odor.  .If  it  is  contaminated  or  drawn  from 
a  swampy  region  it  may  be  somewhat  moldy  or  unpleasant. 

Almost  all  surface-waters  have  some  odor.  Many  times 
it  is  too  faint  to  be  noticed  by  the  ordinary  consumer,  though 

117 


Il8  THE  MICROSCOPY  OF  DRINKING-WATER. 

it  can  be  detected  by  one  whose  sense  of  smell  is  carefully 
trained.  On  the  other  hand,  the  water  in  a  pond  may  have 
so  strong  an  odor  that  it  is  offensive  several  hundred  feet 
away.  Between  these  two  extremes  one  meets  with  odors 
that  vary  in  intensity  and  in  character,  and  that  are  often  the 
source  of  much  annoyance  and  complaint. 

It  is  difficult  to  classify  the  odors  of  surface-waters  on  a 
satisfactory  basis,  but  they  fall  into  three  general  groups: 
I.  Odors  caused  by  organic  matter  other  than  living  organ- 
isms. 2.  Odors  caused  by  the  decomposition  of  organic 
matter.  3.  Odors  caused  by  living  organisms. 

I.  The  odors  caused  by  organic  matter  other  than  living 
organisms  may  be  included  under  the  general  term  vegetable. 
They  vary  in  character  in  different  waters  and  at  different 
seasons.  It  is  difficult  to  find  terms  that  will  describe  them 
exactly.  It  is  seldom  that  two  observers  will  agree  as  to  the 
most  appropriate  descriptive  adjective.  To  one  person  the 
odor  of  a  water  may  be  straw-like,  to  another  swamp-like,  to 
another  peaty.  This  is  due  to  the  fact  that  the  sense  of  smell 
in  man  is  not  well  cultivated.  In  practice,  therefore,  it 
has  become  customary  to  use  the  general  term  vegetable 
instead  of  the  terms  straw-like,  swamp-like,  marshy,  peaty, 
sweetish,  etc.  The  intensity  of  an  odor  may  be  indicated  by 
using  the  prefixes  very  faint,  faint,  distinct,  decided,  very 
strong.  A  better  method,  however,  is  to  use  numerical  pre- 
fixes, which  may  be  approximately  defined  as  shown  in  table 
on  p.  119.  According  to  this  method  the  expression  "  3  f " 
would  indicate  a  ' '  distinct  fishy  odor, "  ' '  2  v  "  a  "  faint  vege- 
table odor,"  etc.  The  reader  will  understand  that  the  above 
definitions  are  far  from  exact,  and  that  the  intensity  of  odors 
varying  in  character  cannot  be  well  compared.  A  faint  fishy 
odor,  for  example,  might  often  attract  more  attention  than  a 
distinct  vegetable  odor.  Heating  a  water  usually  intensifies 


ODORS  IN    WATER  SUPPLIES. 


Numerical  Value. 

Term. 

Approximate  Definition. 

0 

None. 

No  odor  perceptible. 

I 

Very  Faint. 

An  odor  that  would  not  be  ordinarily  detected 
by  the  average  consumer,  but  that  could 
be  detected  in  the  laboratory  by  an  ex- 
perienced observer. 

2 

Faint. 

An  odor  that  the  consumer  might  detect  if 
his  attention  were  called  to  it,  but  that 
would  not  otherwise  attract  attention. 

3 

Distinct. 

An  odor  that  would  be  readily  detected  and 
that  might  cause  the  water  to  be  regarded 
with  disfavor. 

4 

Decided. 

An  odor  that  would  force  itself  upon  the 
attention  and  that  might  make  the  water 
unpalatable. 

5 

Very  Strong. 

An  odor  of  such  intensity  that  the  water 
would  be  absolutely  unfit  to  drink,  (a 
term  to  be  used  only  in  extreme  cases). 

its  odor.*     A  water  that  has  a  faint  odor  when   cold  may 
have  a  distinct  odor  when  hot. 

Most  of  the  vegetable  odors  are  caused  by  vegetable  matter 
in  solution.  Brown-colored  waters  invariably  have  a  sweetish- 
vegetable  odor,  and  the  intensity  of  the  odor  varies  almost 
directly  with  the  depth  of  the  color.  Both  color  and  odor 
are  due  to  the  presence  of  certain  glucosides,  of  which  tannin 
is  an  example,  extracted  from  leaves,  grasses,  mosses,  etc. 
In  addition  to  the  odor,  these  substances  have  a  slight 
astringent  taste.  Colorless  waters  containing  organic  matter 
of  other  origin  may  have  vegetable  odors,  but  they  are  usually 
less  sweetish  and  more  straw-like  or  peaty.  Akin  to  the 
vegetable  odors  are  the  earthy  odors  caused  by  finely  divided 

*  In  the  laborator)"  the  "cold  odor"  is  observed  by  shaking  a  partly 
filled  bottle  of  the  water  and  immediately  removing  the  stopper  and  apply- 
ing the  nose.  The  "hot  odor  "is  obtained  by  heating  a  portion  of  the 
water  in  a  tall  beaker  covered  with  a  watch-glass  to  a  point  just  short  of 
boiling.  When  sufficiently  cool  the  cover  is  slipped  aside  and  the  observa- 
tion made. 


120  THE   MICROSCOPY   OF  DRINKING-WATER. 

particles  of    organic  matter,   clay,   etc.     The  two  odors  are 
often  associated  in  the  same  sample. 

2.  Odors  produced  by  the  decomposition  of  organic  matter 
in  water  are  not  uncommon.      They  are  described,  somewhat 
imperfectly,    by    such    terms    as    moldy,    musty,    unpleasant,, 
disagreeable,  offensive.     An  unpleasant  odor  is  produced  when 
the  vegetable  matter  in  water  begins  to  decay.      It  may  be 
said    to    represent    the    first    stages    of    decomposition.     As 
decomposition  progresses  the  unpleasant  odors  become  dis- 
agreeable, and  then  offensive.     It  is  seldom  that  the  decom- 
position of  vegetable  matter  in  water  produces  odors  worse 
than  "decidedly  unpleasant."     The  disagreeable  odors  usually 
can  be  traced  to  decaying  animal  matter,  and,  as  a  rule,  offen- 
sive odors  are  observed  only  in  sewage  or  in  grossly  polluted 
water.     The  terms  moldy  and  musty  are  more  specific  than 
the  terms  unpleasant,  disagreeable,  and  offensive,  but  they  are 
difficult  to  define.     They  are  quite  similar  in  character;  but 
the  musty  odor  is  more  intense  and  is  usually  applied  only  to 
sewage-polluted  water.     The  moldy  odor  suggests   a    damp 
cellar,  or  perhaps  a   decaying  tree-trunk  in  a   forest.     The 
bacteriologist  will  recognize  this  odor  as  similar  to  that  given 
off  by  certain  bacteria  growing  on  nutrient  gelatine. 

The  odors  of  decomposition  naturally  are  associated  with 
the  odors  of  the  other  groups,  and  one  often  finds  it  conven- 
ient to  use  such  expressions  as  "distinctly  vegetable  and  faintly 
moldy,"  i.e.,  "3v-f-2m,"  or  *'  decidedly  fishy  and  disagree- 
able," i.e.,  "4f  +  4d." 

3.  The  odors  of  drinking-water  due  to  the  presence   of 
living  organisms  are  the   most   important   because   of  their 
common  occurrence,   because  of  their  offensive  nature,   and 
because  they  affect  large  bodies  of  water.     It  is  only  within 
recent  years  that  these  odors  have  been  well  understood,  and 
even  now  there  is  much  to  be  learned  about  the  chemical 


ODORS  IN    WATER-SUPPLIES.  121 

nature  of  the  odoriferous  substances  and  their  relation  to  the 
life  of  the  organisms.  At  one  time  it  was  supposed  that  it 
was  only  by  decay  that  the  organisms  became  offensive. 
It  is  now  a  well-established  fact  that  many  living  organ- 
isms have  an  odor  that  is  natural  to  them  and  that  is  pecul- 
iar to  them,  just  as  a  fresh  rose  or  an  onion  has  a  natural 
and  peculiar  odor.  It  has  been  found,  also,  that  in  most 
cases, — and  it  may  be  true  in  all  cases, — the  odor  is  produced 
by  compounds  analogous  to  the  essential  oils.  In  some  cases; 
the  oily  compounds  have  been  isolated  by  extraction  with. 
ether  or  gasoline.  Odors  due  to  these  oils  have  been  called 
" odors  of  growth"  because  the  oils  are  produced  during  the 
growth  of  the  organisms.  The  oil-globules  may  be  seen  in 
many  genera  if  they  are  examined  with  a  sufficiently  high 
power.  They  are  usually  most  numerous  in  the  mature  forms 
and  are  often  particularly  abundant  just  before  sporulation  or 
encystment.  The  production  of  the  oil  represents  a  stor- 
ing-up  of  energy.  The  odors  have  been  called  " odors  of 
disintegration,"  because  they  are  most  noticeable  when  the 
breaking  up  of  the  organism  causes  the  oil-globules  to  be 
scattered  through  the  water.  It  is  sufficient,  however,  to  call 
them  the  "natural  odors"  of  the  organisms,  to  distinguish 
them  from  the  very  different  odors  produced  by  their  decom- 
position. 

It  was  stated  in  Chapter  IV  that  the  microscopic  organ- 
isms are  not  found  in  ground-waters  (except  when  stored  in 
open  reservoirs)  nor  in  streams  in  sufficient  abundance  to 
cause  trouble.  It  is  in  the  quiescent  waters  of  ponds  and 
lakes  and  reservoirs  that  they  develop  luxuriantly,  and  it  is  to 
the  reservoir  that  one  should  look  first  when  investigating  the 
cause  of  an  odor  in  a  public  water-supply. 

The  littoral  organisms  found  on  the  sides   of  reservoirs. 


122  THE   MICROSCOPY   OF  DRINKING-WATER 

include  the  flowering  aquatic  plants,  the  Characeae,  the 
filamentous  algae,  etc.,  of  the  vegetable  kingdom  and  the 
fresh-water  sponge,  Bryozoa,  etc.,  of  the  animal  kingdom. 
The  effect  which  they  exert  on  the  odor  of  a  water  is  difficult 
to  determine  because  they  are  seldom  found  in  a  reservoir 
where  the  floating  microscopic  organisms  are  absent.  In 
many  cases  where  a  peculiar  odor  of  a  water  has  been  charged 
to  some  of  these  littoral  forms,  subsequent  investigation  has 
made  it  probable  that  the  odor  was  really  caused  by  limnetic 
organisms  that  had  been  overlooked  in  the  first  instance. 

Speaking  generally  it  may  be  said  that  in  reservoirs  that 
are  large  and  deep  the  organisms  attached  to  the  shores  pro- 
duce little  or  no  effect  on  the  odor  of  the  water;  and  that  in 
small  shallow  reservoirs  where  the  aquatic  vegetation  is  thick 
they  do  not  impart  any  characteristic  " natural"  odor,  but 
they  may  produce  a  sort  of  vegetable  taste  and  a  disagreeable 
odor  due  to  decomposition. 

Some  of  the  littoral  aquatic  plants,  such  as  Myriophyllum 
and  a  number  of  the  filamentous  algae,  possess  a  natural  odor 
that  is  strongly  "  vegetable"  and,  at  times,  almost  fishy; 
but  the  odor  is  obtained  only  when  the  plants  are  crushed  or 
when  fragments  are  broken  off  and  scattered  through  the 
water.  Under  ordinary  conditions  of  growth  in  a  reservoir 
this  does  not  happen  and  therefore  no  odor  is  imparted  to  the 
water  except  through  decomposition. 

There  are  on  record  some  apparent  exceptions  to  the  rule 
that  the  attached  growths  cause  no  odor.  Hyatt  *  described  a 
growth  of  Meridion  circulare  at  the  headwaters  of  the  Croton 
River,  in  1881,  that  was  supposed  to  have  affected  the  entire 
supply  of  New  York  City:  Rafter  has  connected  odors  with 

*  References  to  this  and  similar  illustrations  may  be  found  in  the  bib- 
liography in  the  appendix. 


ODORS   IN    WATER-SUPPLIES.  12$ 

Hydrodictyon  utriculatum  and  other  Chloropbyceae:  Forbes 
investigated  a  water-supply  where  a  growth  of  Chara  was 
thought  to  be  the  cause  of  a  bad  odor;  and  Western  has 
stated  that  serious  trouble  was  caused  in  Henderson,  N.  C., 
by  an  extensive  growth  of  Cristatella.*  All  of  these  cases 
where  odors  in  water-supplies  have  been  attributed  to  certain 
limnetic  organisms  lack  corroboration. 

The  author  once  examined  a  reservoir  where  a  mass  of 
Melosira  varians  several  feet  thick  covered  the  slopes  to  a  con- 
siderable depth.  A  severe  storm  tore  away  the  fragile  fila- 
ments, and  masses  of  Melosira  passed  into  the  distribution-pipes 
and  caused  a  noticeable  vegetable  and  oily  odor  in  the  water. 

In  connection  with  the  relation  of  the  littoral  organisms 
to  odors  in  water-supplies  some  reference  should  be  made 
to  the  " cucumber  taste"  that  has  been  a  frequent  cause 
of  complaint  against  the  Boston  water-supply.  In  1881  the 
trouble  was  very  severe.  The  water  had  a  decided  odor  of 
cucumbers,  which  was  intensified  at  times  to  a  "fish-oil" 
odor.  Heating  made  the  odor  very  strong  and  offensive. 
A  noted  expert  made  an  examination  and  concluded  that  the 
seat  of  the  trouble  was  in  Farm  Pond, — one  of  the  sources  of 
supply.  This  pond  was  so  situated  that  all  the  water  of  the 
Sudbury  system  passed  through  it  on  its  way  to  the  city. 
Chemical  analysis  of  the  water  and  microscopical  examination 
of  the  mud  failed  to  reveal  the  cause  of  the  odor.  It  was 
found,  however,  that  fragments  of  fresh-water  sponge  (Spon- 
gilla  fluviatalis)  were  constantly  collecting  on  the  screens 
and  that  these  had  the  "cucumber  odor."  It  was  decided 
therefore  that  the  fresh-water  sponge  was  the  cause  of  the 
odor.  The  conclusion  was  quite  generally  accepted  and  the 
report  has  been. quoted  extensively. 

*  The  organism  observed  was  probably   Pectinatella  and   not  Crista- 
iella. — AUTHOR. 


124  THE   MICROSCOPY   OF  DRINKING-WATER. 

At  that  time  some  water  experts  disagreed  with  this  opin- 
ion. They  claimed  that  the  amount  of  sponge  found  in  the 
pond  was  not  sufficient  to  produce  the  odor.  In  the  light  of 
modern  microscopical  examinations  we  are  coming  to  believe 
that  the  dissenters  were  right  and  that  the  fresh-water  sponge 
was  not  the  cause  of  the  cucumber  odor.  The  author  has  taken 
masses  of  Spongilla  and  allowed  them  to  rot  in  a  small  quan- 
tity of  water  till  the  odor  was  unbearable.  This  water  was 
then  diluted  with  distilled  water  to  see  how  large  a  mass  of 
water  the  decayed  sponge  would  affect.  It  was  found  that 
with  a  dilution  of  I  to  50  ooo  there  was  no  perceptible  odor. 
If  this  is  true  it  would  take  a  mass  of  sponge  several  feet 
thick  over  the  entire  bottom  of  Farm  Pond  to  produce  an 
odor  as  intense  as  that  observed  in  1881.  Morever  the  odor 
produced  by  the  sponge  is  not  the  ' 'cucumber  odor, "  although 
it  is  similar  to  it. 

There  is  good  reason  to  believe  that  the  cucumber  odor 
observed  in  1881  was  due  to  Synura.  One  need  not  dispute 
the  observation  that  the  sponge  that  collected  on  the  Farm 
Pond  screens  had  the  cucumber  odor,  for  no  doubt  the 
sponge  was  covered  with  Synura,  as  it  is  often  covered  with 
other  organisms.  It  is  not  surprising,  either,  that  the  Synura 
should  have  been  overlooked  in  the  water,  because  the  organ- 
ism disintegrates  readily  and  a  comparatively  small  number  of 
colonies  is  able  to  produce  a  considerable  odor.  The  times 
of  the  occurrence  of  the  odor — namely,  in  the  spring  and 
autumn — are  worth  noting,  as  they  correspond  with  the 
seasons  when  Synura  grows  best  and  when  it  is  most  com- 
monly found. 

In  February,  1892,  the  cucumber  taste  again  appeared  in 
the  Boston  water.  This  time  it  was  definitely  traced  to 
Synura  that  was  growing  in  the  water  just  under  the  ice  in 


ODORS   IN    WATER-SUPPLIES.  12$ 

Lake  Cochituate.  Since  then  it  has  reapppeared  at  intervals 
in  other  parts  of  the  supply, — notably  in  Basin  3  and  Basin  6. 
It  has  been  found  that  5  or  10  colonies  per  c.c.  are  sufficient 
to  cause  a  perceptible  odor. 

The  floating  microscopic  organisms,  or  the  plankton,  are 
responsible  for  most  of  those  peculiar  nauseating  odors  that 
are  the  cause  of  complaint  in  so  many  public  water-supplies. 
In  most,  if  not  in  all,  cases  the  odor  is  due  to  the  presence  of 
an  oily  substance  elaborated  by  the  organisms  during  their 
growth.  This  has  been  proved  by  long-continued  observa- 
tions and  experiments,  during  the  course  of  which  the  follow- 
ing facts  have  been  noted : 

The  odors  referred  to  vary  in  character.  They  are  difficult 
to  describe,  but  they  can  be  readily  identified.  Particular 
odors  are  associated  with  particular  organisms.  If  an  organ- 
ism is  present  in  sufficient  numbers  its  particular  odor  will  be 
observed ;  if  it  is  not  present  in  sufficient  numbers  its  odor 
will  not  be  observed.  Further,  the  intensity  of  the  odor 
varies  with  the  number*  of  organisms  present.  If  water 
that  contains  an  organism  which  has  a  natural  odor  is  filtered 
through  paper,  the  odor  of  the  filtered  water  f  will  be  much 
fainter  than  before,  and  the  filter-paper  on  which  the  organ- 
isms remain  will  have  a  strong  odor.  If  the  organisms  are 
concentrated  by  the  Sedgwick-Rafter  method,  the  concentrate 
will  have  a  decided  taste  and  odor.  If  these  organisms  are 
placed  in  distilled  water,  the  water  will  acquire  the  odor  of  the 
original  water.  Thus,  the  relation  between  particular  odors 
and  particular  organisms  has  been  well  established.  Indeed, 
in  the  absence  of  a  microscopical  examination,  experienced 

*  There  are  some  exceptions  to  this. 

f  In  some  cases  the  odoriferous  substances  from  the  organisms  pass 
through  the  filter,  and  the  disintegration  of  the  organisms  gives  the  filtered 
water  an  increased  odor  over  the  unfiltered  water- 


126  THE   MICROSCOPY   OF  DRINKING-WATER. 

observers  are  often  able  to  tell  the  nature  of  the  organisms 
present  by  a  simple  observation  of  the  odor. 

That  the  odors  are  not  due  to  the  decomposition  of  the 
organism  is  proved  by  the  character  of  the  odors  themselves 
and  by  the  fact  that  they  are  not  accompanied  necessarily  by 
large  numbers  of  bacteria  or  by  the  presence  of  free  ammonia 
or  nitrites.  This  is  supported  by  the  fact  that,  when  the 
organisms  do  decay,  the  bacteria  increase  in  number  and  the 
odor  of  the  water  changes  in  character. 

The  natural  odor  is  given  off  by  some  substance  inside  of 
the  organism,  and  when  this  substance  becomes  liberated  the 
odor  is  more  easily  detected.  The  odor  is  intensified  by  heat- 
ing, by  mechanical  agitation,  and  by  change  in  the  density  of 
the  water  containing  the  organisms.  Many  of  the  odor-pro- 
ducing organisms  are  very  delicate.  Heating  breaks  them  up 
and  drives  off  the  odoriferous  substances.  The  flow  of  water 
through  the  pipes  of  a  distribution  system  is  sufficient  to  cause 
the  disintegration  of  many  forms,  and  it  is  a  matter  of  common 
observation  that  in  such  cases  the  odor  of  a  water  at  the 
service-taps  is  more  pronounced  than  at  the  reservoir.  If 
the  density  of  a  water  is  increased  by  adding  to  it  some  sub- 
stance, such  as  salt,  the  organisms  may  become  distorted 
if  not  actually  broken  up.  This  causes  an  intensification 
of  their  odor.  Increased  pressure  also  leads  to  the  same 
result. 

The  natural  odor  of  the  organisms  is  due  to  some  oily 
substance  analogous  to  those  substances  found  in  higher  plants 
and  animals,  and  that  give  the  odor  to  the  peppermint  and 
the  herring.  The  fact  was  noted  long  ago  that  the  addition 
of  salt  to  water  that  was  affected  with  certain  odors  developed 
nil  oily  flavor.  Many  of  the  odors  caused  by  organisms  are 
of  a  marked  oily  nature.  The  oil-globules  in  these  organ- 


ODORS   IN    WATER-SUPPLIES.  I2/ 

isms  may  be  observed  with  the  microscope.  The  number  of 
oil-globules  varies  according  to  the  age  and  condition  of  the 
organisms,  and  the  intensity  of  the  odor  varies  with  the 
number  of  oil-globules  present.  Finally,  the  oily  substances 
have  been  extracted  from  the  organisms  and  it  has  been 
found  that  they  possess  the  same  odor  as  that  observed  in 
the  water  containing  them. 

A  series  of  experiments  was  made  at  one  time  to  show 
that  the  amount  of  oil  present  in  the  organisms  was  sufficient 
to  account  for  the  odors  observed  in  drinking-water.  Some 
of  the  familiar  essential  oils,  such  as  oil  of  peppermint, 
oil  of  clove,  cod-liver  oil,  etc.,  were  diluted  with  distilled 
water,  and  the  amount  of  dilution  at  which  the  odor  be- 
came unrecognizable  was  noted.  The  oil  of  peppermint 
was  recognized  when  diluted  I  :  50000000;  the  oil  of  clove, 
I  :  8000000;  cod-liver  oil,  I  :  IOOOOOO;  etc.  The  odor  of 
kerosene  oil  could  not  be  detected  when  diluted  I  :  800  ooo. 
The  amount  of  oil  present  in  water  containing  a  known  num- 
ber of  organisms  was  estimated  for  comparison.  It  was  found 
that  in  water  containing  100  colonies  of  Synura  per  c.c.  the 
dilution  of  the  Synura  oil  was  I  :  25  ooo  OOO;  and  that  in  a 
water  with  50000  Asterionella  per  c.c.  the  dilution  was  only 
I  :  2  ooo  ooo.  Thus,  the  production  of  the  odor  by  the  oil 
is  quite  within  the  range  of  possibility.  An  interesting  fact 
brought  out  by  the  experiments  was  that  the  odor  of  the  oils 
varied  with  different  degrees  of  dilution  not  only  in  intensity 
but  in  character.*  This  variation  of  the  character  of  the 
odor  with  its  intensity  is  important  to  notice,  as  it  accounts 
for  the  different  descriptions  of  the  same  odor  in  a  water- 
supply  at  different  times  and  by  different  people. 

*  On  one  occasion  seven  people  out  of  ten  who  were  asked  to  observe 
the  odor  of  very  highly  diluted  kerosene  oil  declared  that  it  smelled  like 
"  perfumery." 


128  THE   MICROSCOPY   OF  DRINKING-WATER. 

The  nature  of  the  odoriferous  oils  or  oily  substances  is 
not  well  known.  Calkins,  who  isolated  the  odoriferous  prin- 
ciple of  Uroglena  with  gasoline  and  ether,  describes  it  as  being 
.similar  to  the  essential  oils.  It  was  non-volatile  at  the  tem- 
perature of  boiling  water.  Jackson  and  Ellms  extracted  a 
similar  substance  from  Anabaena  with  gasoline.  On  standing 
it  oxidized  and  became  resinous.  It  contained  needle-like 
•crystals.  Experiments  by  the  author  have  shown  that  the 
oils  of  Asterionella  and  Mallomonas  are  quite  similar  in  char- 
acter. 

Most,  if  not  all,  of  the  organisms  produce  oil  during  their 
growth  to  a  greater  or  less  degree.  In  many  cases  it  is  quite 
odorless.  Water  is  often  without  odor  even  when  large  num- 
bers of  organisms  are  present.  This  is  either  because  the 
organisms  have  not  produced  oil,  or  because  the  oil  is  odor- 
less. Sometimes  water  rich  in  organisms  will  have  an  oily 
flavor  with  no  distinctive  odor.  This  is  true  in  the  case  of 
some  species  of  Melosira.  Many  organisms  impart  a  vegetable 
and  oily  taste,  without  a  distinctive  odor.  This  is  true  of 
Synedra  pulchella  and  Stephanodiscus.  There  are,  moreover, 
microscopic  organisms  that  produce  oils  that  have  a  distinc- 
tive odor,  but  that  occur  in  drinking-water  in  such  small  num- 
bers that  the  odor  is  not  detected.  The  organisms  that  have 
a  distinctive  odor  and  that  are  found  in  large  numbers  are 
comparatively  few.  Not  more  than  twenty-five  have  been 
recorded  and  only  about  half  a  dozen  have  given  serious 
trouble.  More  extended  observations  may  lengthen  this 
list. 

The  distinctive  odors  produced  by  these  organisms  may 
be  grouped  around  three  general  terms, — aromatic,  grassy, 
and  fishy, — and  for  convenience  they  may  be  tabulated  as 
follows: 


ODORS   IN    WATER-SUPPLIES. 


I29 


Group. 


Organism. 


Natural  Odor. 


AROMATIC 
ODOR. 


GRASSY 
ODOR. 


FISHY 
ODOR. 


DlATOMACE^E 

Asterionella 
Cyclotella 
Diatoma 
Meridion 
Tabellaria 
PROTOZOA 
Cryptomonas 
Mallomonas 

CYANOPHYCE^E 
Anabaena 

Rivularia 
Clathrocystis 
Coelosphaerium 
Aphanizomenon 

CHLOROPHYCE^ 

Volvox 

Eudorina 

Pandorina 

Dictyosphaerium 
PROTOZOA 

Uroglena 

Synura 

Dinobryon 

Bursaria 

Peridinium 

Glenodinium 


Aromatic — geranium- 
Faintly  aromatic. 

Aromatic. 


-fishy. 


Candied  violets. 
Aromatic — violets — fishy. 


Grassy  and    moldy — green-corn — nas- 
turtiums, etc. 
Grassy  and  moldy. 
Sweet,  grassy. 

Grassy. 


Fishy. 
Faintly  fishy. 


Fishy  and  oily. 

Ripe  cucumbers — bitter  and  spicy  taste. 

Fishy,  like  rockweed. 

Irish  moss — salt  marsh — fishy. 

Fishy,  like  clam-shells. 

Fishy. 


The  aromatic  odors  are  due  chiefly  to  the  Diatomaceae. 
The  strongest  odor  is  that  produced  by  Asterionella.  The 
character  of  this  odor  changes  with  its  intensity.  When  few 
organisms  are  present  the  water  may  have  an  undefinable 
aromatic  odor;  as  they  increase  the  odor  resembles  that  of  a 
rose  geranium;  when  they  are  very  abundant  the  odor  becomes 
fishy  and  nauseating.  The  other  diatoms  given  in  the  table 
produce  the  aromatic  odor  only  when  present  in  very  large 
numbers.  There  are  two  Protozoa  that  have  an  aromatic 
odor.  The  odor  of  Cryptomonas  is  sweetish  and  resembles 
that  of  the  violet.  The  odor  of  Mallomonas  is  similar  to  that 
of  Cryptomonas,  but  when  strong  it  becomes  fishy. 


13°  THE   MICROSCOPY   OF  DRINKING-WATER. 

The  grassy  odors  are  produced  by  the  Cyanophyceae. 
Anabaena  is  the  most  important  organism  of  this  class.  There 
are  several  species  that  have  slightly  different  odors.  The 
grassy  odor  is  usually  accompanied  by  a  moldy  odor,  which  is 
probably  due  to  decomposition,  as  this  organism  decays 
rapidly.  When  very  strong  the  odor  of  Anabaena  much  re- 
sembles raw  green-corn,  or  even  a  nasturtium  stem.  The 
prevailing  odor,  however,  is  grassy,  i.e.  the  odor  of  freshly 
cut  grass.  The  other  blue^green  algae  have  odors  that  may 
be  called  grassy,  but  they  are  less  distinctive  than  in  the  case 
of  Anabaena. 

The  fishy  odors  are  the  most  disagreeable  of  any 
observed  in  drinking-water.  That  produced  by  Uroglena  is 
perhaps  the  worst.  It  is  quite  common.  Water  rich  in 
Uroglena  has  an  odor  not  unlike  that  of  cod-liver  oil.  The 
odor  of  Synura  is  almost  as  bad  and  almost  as  common.  It 
resembles  that  of  a  ripe  cucumber.  Synura  also  has  a  distinct 
bitter  and  spicy  taste.  It  "stays  in  the  mouth  "  and  is  most 
noticeable  at  the  back  part  of  the  tongue.  Glenodinium  and 
Peridinium  both  produce  fishy  odors.  The  latter  somewhat 
resembles  clam-shells.  Dinobryon  has  a  fishy  odor  and  sug- 
gests sea-weed.  The  odor  of  Bursaria  is  like  that  of  Irish 
moss.  It  also  reminds  one  of  a  salt  marsh.  With  certain 
degrees  of  dilution  some  other  Protozoa  have  the  salt-marsh 
odor,  reminding  one  of  the  sea.  Fishy  odors  are  said  to 
be  produced  by  Volvox,  Eudorina,  and  Pandorina.  These 
Chlorophyceae  are  sometimes  classed  with  the  Protozoa,  so 
that  it  may  be  said  in  a  general  way  that  the  fishy  odors  are 
produced  by  microscopic  organisms  belonging  to  the  animal 
kingdom. 

Some  of  the  microscopic  organisms  have  distinctive  odors 
of  decomposition.  The  Cyanophyceae  when  decaying  give  a 


ODORS   IN    WATER-SUPPLIES.  131 

"pig-pen  "  odor.  Beggiatoa  and  some  species  of  Chara  give 
the  odor  of  sulphuretted  hydrogen.  All  the  odors  given  off 
by  the  decomposition  of  microscopic  organisms  are  offensive. 
They  are  particularly  so  when  the  organisms  contain  a  high 
percentage  of  nitrogen.  Jackson  and  Ellms,  in  an  interesting 
study  of  the  decomposition  of  Anabaena  circinnalis,  found 
that  that  organism  contained  9.66$  of  nitrogen.  They  found 
that  the  "pig-pen  "  odor  was  due  "to  the  breaking  down  of 
highly  organized  compounds  of  sulphur  and  phosphorus  and 
to  the  presence  of  this  high  percentage  of  nitrogen.  The 
gas  given  off  during  decomposition  was  found  to  have  the 
following  composition : 

Marsh-gas 0.8$ 

Carbonic  acid 1.5$ 

Oxygen    2.9$ 

Nitrogen    12.4$ 

Hydrogen 82 .4^ 


1  00. 


The  gas  that  remained  dissolved  in  the  water  containing  the 
Anabaena  was  practically  all  CO2  and  represented  a  large  per- 
centage of  the  total  gas  produced." 

Besides  the  odors  above  described,  water-supplies  some- 
times become  affected  with  what  have  been  called  "chemical 
odors,"  —  such  as  those  of  carbolic  acid,  creosote,  tar,  etc. 
They  can  be  traced  usually  to  some  pollution  by  manufactur- 
ing waste,  though  a  vigorous  decomposition  of  organic  matter 
has  been  known  to  give  an  odor  resembling  carbolic  acid. 
Similar  odors  are  sometimes  caused  by  the  coating  on  the 
inside  of  new  distribution-pipes. 

The  extent  to  which  water-supplies  are  afflicted  with  odors 


132  THE   MICROSCOPY   OF  DRINKING-WATER. 

was  well  shown  by  the  investigations  of  the  Massachusetts 
State  Board  of  Health.  Out  of  71  water-supplies  taken  from 
ponds  and  reservoirs,  45,  or  63$,  were  found  to  have  given 
trouble  from  bad  tastes  or  odors,  and  about  two  thirds, of 
these  had  given  serious  trouble.  Calkins  has  stated  that  in 
1404  samples  from  surface-water  supplies  in  Massachusetts 
odors  were  observed  as  follows: 

Odor.  Per  Cent  of 

Samples  Affected. 

No  odor to 20 

Vegetable 26 

Sweetish 7 

Aromatic 6 

Grassy 15 

;.;..   Fishy 3 

Moldy 10 

Disagreeable 6 

Offensive 7 

The  intensity  of  these  odors  was  not  stated.  Many  of 
them  probably  were  not  strong  enough  to  cause  complaint. 

It  must  not  be  inferred  from  this  that  Massachusetts  is 
more  afflicted  in  her  surface-water  supplies  than  other  sections 
of  the  country.  The  same  troubles  are  observed  everywhere. 
It  is  only  because  the  Massachusetts  supplies  have  been  more 
carefully  studied  than  elsewhere  that  attention  has  been 
drawn  to  them.  In  a  previous  chapter  it  was  stated  that  the 
microscopic  organisms  are  widely  distributed  both  in  this 
country  and  abroad.  Wherever  they  are  found  in  abundance 
they  must  inevitably  affect  the  odor  of  the  water. 

The  question  is  often  asked,  "  Are  growths  of  organisms 
such  as  Asterionella,  Synura,  etc.,  injurious  to  health?" 
This  cannot  be  answered  authoritatively,  but  from  the  data 


ODORS  IN    WATER-SUPPLIES. 


133 


at  hand  it  is  believed  that  such  organisms  are  not  injurious, — 
certainly  not  to  persons  in  good  health.  The  actual  amount 
of  solid  matter  contained  in  the  organisms  is  much  smaller 
than  might  be  supposed.  For  example,  it  has  been  calculated 
that  the  weight  of  one  Asterionella  is  .0000000004  gram.  A 
growth  of  100000  Asterionella  per  c.c.  would  render  a  water 
unfit  to  drink  because  of  its  odor,  yet  a  tumblerful  of  such 
water  would  contain  but  eight  milligrams  of  solid  matter,  and 
only  one  half  of  this  would  be  organic  matter.  It  is  almost  in- 
conceivable that  such  a  small  amount  of  organic  matter  could 
cause  trouble  unless  some  poisonous  principle  were  present, 
and  so  far  as  is  known  no  such  substance  has  been  found. 
The  alleged  cases  of  poisonous  algae  rest  upon  too  uncertain 
evidence  to  be  received  as  facts. 

Nevertheless  there  is  some  reason  to  believe  that  people 
accustomed  to  drinking-water  free  from  organisms  may  be 
subjected  to  temporary  intestinal  disorders  when  they  begin 
to  drink  water  rich  in  microscopic  organisms, — just  as  people 
are  affected  by  changing  from  a  hard  to  a  soft  water  and  vice 
versa.  It  is  possible  that  with  young  children  and  invalids 
such  disorders  may  be  more  common  than  has  been  supposed. 


CHAPTER    X. 
STORAGE   OF   SURFACE-WATER. 

To  obtain  a  permanently  safe  and  satisfactory  surface- 
water  supply  without  filtration  the  rainfall  must  be  collected 
quickly  from  a  clean  watershed  and  stored  in  a  clean  reservoir. 

A  clean  watershed  may  be  defined  as  one  upon  which 
there  are  no  sources  of  pollution  and  no  accumulations  of 
decomposing  organic  matter.  The  subject  of  pollution  is  of 
paramount  importance,  but  it  will  not  be  emphasized  here  as 
its  discussion  leads  into  bacteriology  rather  than  into  micros- 
copy. No  watershed  can  be  free  from  organic  matter,  and 
this  must  eventually  decompose.  The  grass  dies,  the  leaves 
fall,  and  a  thin  layer  of  decay  is  spread  over  the  surface 
of  the  ground.  This  is  repeated  each  season.  Normally 
this  organic  matter  disappears  by  rapid  oxidation,  and  if 
the  ground  is  sloping  the  rain  that  falls  upon  it  runs  off 
rapidly  and  absorbs  comparatively  little  organic  matter.  If, 
however,  the  decaying  vegetation  has  accumulated  in  thick 
layers,  if  the  ground  is  level  and  becomes  saturated  or  covered 
with  water,  decomposition  takes  place  under  different  condi- 
tions, and  the  water  may  become  highly  charged  with  organic 
matter  and  the  products  of  decay. 

The  effect  of  swamp  areas  upon  the  color  of  water  has 
been  referred  to.  Water  from  a  clean  watershed  seldom 
has  a  color  higher  than  30  of  the  Platinum  Scale.  The 

134 


STORAGE    OF  SURFACE-WATER.  13$ 

-amount  of  color  above  this  figure  can  be  generally  traced  to 
swampy  land.  The  color  of  the  stagnant  water  of  swamps 
is  sometimes  very  high, — often  300  and  sometimes  as  high  as 
500  or  700  on  the  Platinum  Scale.  From  this  it  is  easy 
to  see  that  even  a  comparatively  small  percentage  of  swamp- 
land upon  a  watershed  may  have  an  important  effect  upon  the 
color  of  the  combined  yield. 

A  highly  colored  water  means  a  water  rich  in  organic 
matter.  If  the  color  is  much  above  50  the  water  has  an 
unsightly  appearance,  a  distinct  vegetable  odor,  and  a 
sweetish  and  somewhat  astringent  taste.  But  the  pres- 
ence of  organic  matter  is  objectionable  for  another  reason. 
It  helps  to  furnish  food-material  for  the  microscopic  organisms, 
and  these  may  render  the  water  very  disagreeable.  Swamps 
are  breeding-places  for  many  of  the  organisms  that  cause 
trouble  in  water-supplies,  and  numerous  instances  might  be 
cited  where  organisms  have  developed  in  a  swamp  and  have 
been  washed  down  into  a  storage-reservoir,  rendering  the 
water  there  almost  unfit  for  use. 

Cedar  Swamp,  at  the  head  of  the  Sudbury  River  of  the 
Boston  water-supply,  furnishes  an  example  of  this.  During 
August,  1892,  Anabaena  developed  abundantly  in  a  small 
pond  in  the  middle  of  this  swamp.  At  one  time  there  were 
.8400  filaments  (about  50  ooo  standard  units)  per  c.c.  A 
heavy  rain  washed  the  Anabaena  down-stream,  and  on  August 
15  there  were  2064  filaments  per  c.c.  at  the  upper  end  of 
Basin  2.  On  August  17  the  water  entering  the  basin  con- 
tained but  600  filaments,  and  a  week  later  it  contained 
none.  The  Anabaena  were  washed  down-stream  in  a  sort 
of  wave.  Basin  2  is  a  long,  narrow  basin.  The  wave  of 
Anabaena  passed  through  the  basin,  down  the  aqueduct, 
through  the  Chestnut  Hill  Reservoir,  and  into  the  service- 


136  THE   MICROSCOPY   OF  DRINKING-WATER.  • 

pipes.  On  August  22  Anabaena  were  first  observed  at  the 
gate-house  at  the  lower  end  of  Basin  2,  where  there  were  647 
filaments  per  c.c.,  and  on  the  following  day  they  appeared  at 
the  terminal  chamber  of  the  conduit  at  Chestnut  Hill  Reser- 
voir, where  there  were  326  filaments  per  c.c.  In  another 
week  they  became  disseminated  through  this  reservoir 
and  were  found  in  the  service-pipes.  As  the  water  from 
Basin  2  passed  towards  the  city  it  became  mixed  with  the 
water  from  other  sources,  so  that  by  the  time  it  reached 
the  consumers  the  Anabaena  were  not  sufficiently  abundant  to 
cause  complaint.  After  the  first  wave  of  Anabaena  had  passed 
through  Basin  2  the  organisms  began  to  increase  through- 
out the  basin,  and  the  growth  continued  for  several  weeks. 
It  was  evident  that  the  water  from  the  swamp  carried  down 
not  only  the  Anabaena  themselves,  but  enough  food-material 
to  support  their  growth  in  the  basin. 

Instances  are  still  more  common  where  organisms  from 
swamps  have  seeded  storage-reservoirs.  Entering  the  reser- 
voir in  comparatively  small  numbers,  the  organisms  fre- 
quently find  in  the  quiet  water  conditions  favorable  to  their 
growth.  Growths  of  some  of  the  Flagellata  may  be  traced 
directly  to  seeding  from  swamps.  The  draining  of  swamps 
makes  a  vast  improvement  in  the  quality  of  the  water  deliv- 
ered from  a  watershed.  In  general  it  should  be  carried  out 
in  such  a  way  that  the  water  falling  upon  the  clean  portions 
of  the  watershed  is  not  obliged  to  pass  through  the  swamp 
before  entering  the  reservoir.  This  may  be  accomplished  by 
a  system  of  marginal  drains  or  canals.  The  lowering  of  the 
water-table  of  a  swamp  also  improves  the  quality  of  the  water 
delivered  from  it. 

Small  mill-ponds  and  other  imperfectly  cleaned  ponds  or 
pools  are  also  frequent  breeding-places  of  microscopic  organ- 


S  TOR  A  GE   OF  S  URFA  CE-  IV A  TER.  I  3  7 

isms.  Again  the  Boston  water-supply  furnishes  an  example* 
A  short  distance  above  Basin  3  there  were  at  one  time 
several  mill-ponds.  These  ponds  were  favorite  habitats  of 
Synura.  These  organisms  were  often  found  there  in  large 
numbers,  and  when  the  water  was  let  down-stream  through 
the  mills  or  when  heavy  rains  caused  the  ponds  to  overflow, 
the  Synura  would  become  numerous  in  Basin  3. 

Thus  it  is  seen  that  in  order  to  avoid  the  growth  of  trouble- 
some organisms  the  water  should  be  delivered  from  a  water- 
shed quickly,  and  should  not  be  allowed  to  stand  in  shallow 
ponds  or  pools  in  contact  with  organic  matter.  As  far  as 
possible  a  watershed  should  be  self-draining.  It  may  be 
added  that  the  storage  reservoir  also  should  be  self-draining. 
It  often  happens,  when  the  bottom  of  a  reservoir  is  uneven, 
that  water  is  left  in  small  pools  as  the  reservoir  is  drawn 
down.  These  pools  are  usually  shallow  and  the  water 
becomes  warm  and  stagnant.  They  often  become  filled  with 
rich  cultures  of  organisms,  and  when  they  overflow  the  organ- 
isms are  scattered  through  the  reservoir.  Such  pools  or 
pockets  should  be  provided  with  an  outlet.  If  this  is  impos- 
sible it  may  be  advisable  to  fill  them  up.  The  author  once 
observed  a  "pocket"  in  a  reservoir  that  was  excavated  to  a 
considerable  depth  for  the  sake  of  removing  all  the  organic 
matter  at  the  bottom.  This  pocket  could  not  be  drained,  and 
during  the  summer  it  became  the  breeding-place  of  Synura 
and  other  Protozoa.  It  would  have  been  better  to  have 
removed  a  portion  of  the  organic  matter  and  to  have  covered 
the  remainder  with  clean  material. 

It  has  been  stated  that  water  should  not  be  allowed  to 
stand  for  any  length  of  time  in  contact  with  organic  matter. 
It  is  quite  as  bad  for  water  to  stand  over  a  swamp  as  it  is  for 
it  to  stand  in  a  swamp.  It  may  be  worse,  for  if  the  water 


338  THE  MICROSCOPY  OF  DRINKING-WATER. 

has  sufficient  depth  the  decomposition  of  the  organic  matter 
at  the  bottom  may  take  place  in  the  absence  of  oxygen,  and 
under  these  conditions  some  of  the  resulting  products  are 
more  easily  taken  up  by  the  water.  This  brings  us  to  the 
consideration  of  the  so-called  "  stagnation  effects." 

Stagnation. — By  the  term  "stagnation  "  is  meant  a  con- 
tinued state  of  quiescence  of  the  lower  layers  of  water  in  a 
lake  or  reservoir  caused  by  thermal  stratification,  as  described 
in  Chapter  V.  During  these  periods  of  quiescence  the  water 
below  the  thermocline,  i.e.  the  stagnant  water,  undergoes 
certain  changes, — the  character  and  amount  of  these  changes 
varying  with  the  nature  of  the  water  and  especially  with  the 
presence  or  absence  of  organic  matter  at  the  bottom  of  the 
reservoir.  Stagnation  may  be  studied  best  in  ponds  where 
there  is  a  considerable  deposit  of  organic  matter  at  the 
bottom,  and  of  such  ponds  Lake  Cochituate  is  an  excellent 
example. 

Near  the  efflux  gate-house  the  lake  has  a  depth  of  60  ft. 
At  the  bottom  there  is  a  layer  of  organic  matter  of  unknown 
thickness.  The  upper  portion  of  this  is  due  to  deposition 
of  organisms  and  other  organic  material  transported  by  the 
water.  The  period  of  summer  stagnation  extends  from  April 
to  November,  and  during  this  time  the  deposit  of  organic 
matter  at  the  bottom  is  accumulating. 

The  changes  that  take  place  in  the  water  at  the  bottom 
of  Lake  Cochituate  during  the  summer  are  shown  in  the  fol- 
lowing table,  where  the  analyses  of  the  water  at  the  surface 
and  bottom  are  compared.  The  most  conspicuous  change  is 
that  of  the  color  (see  Fig.  18).  While  the  water  at  the  sur- 
face is  bleaching  under  the  action  of  the  sunlight,  that  at  the 
bottom  grows  rapidly  darker  until,  near  the  close  of  the 
stagnation  period,  it  has  a  decided  opalescent  turbidity  and  a 


STORAGE   OF  SURFACE-WATER. 


139 


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140 


THE   MICROSCOPY   OF  DRINKING-WATER. 


rich  brown  color.  A  peculiarity  of  the  water  is  that  its  color 
deepens  rapidly  after  being  drawn  to  the  surface.  These 
color  phenomena  are  due  to  the  presence  of  iron  in  the  water. 
By  sedimentation  of  iron  in  combination  with  organic  matter 
and  of  ferric  hydrate  produced  by  oxidation  in  the  upper 
layers,  a  considerable  deposit  of  iron  has  been  formed  at  the 
bottom.  As  the  oxygen  dissolved  in  the  water  at  the  bottom 
disappears  during  the  summer,  the  ferric  iron  gives  up  its 


DIAGRAM  SHOWING  THE  RELATIONS 
BETWEEN  THE  DIATOM  GROWTHS  AND 
THE  STAGNATION  AND  CIRCULATION 
OF  THE  WATER  IN  LAKE  COCHJTUATE. 


DIATOMS 
AVERAGE  NUM 
PER  C.  C.  FOR 
SURFACE,  MID-OEPTH 
AND    BOTTOM. 


JULY  AUG.  SEP.  OCT.  NOV.  DEC. 


FIG.  1 8. — STAGNATION  EFFECTS — LAKE  COCHITUATE. 

oxygen  to  the  organic  matter  and  becomes  reduced  to  the 
ferrous  state.  In  this  state  it  is  soluble.  As  stagnation  con- 
tinues it  becomes  dissolved  in  increasing  amounts.  When 
carried  to  the  surface  it  becomes  oxidized  to  the  insoluble 
ferric  state,  deepening  the  color  of  the  water  for  a  time,  but 
later  precipitating  as  a  brown  sediment  and  leaving  the  water 


S  TOR  A  GE   OF  S  URFA  CE-  IV A  TER.  1 4 1 

with  little  color.  Important  changes  in  the  organic  matter 
in  the  lower  layers  take  place  during  the  stagnation  periods. 
The  amount  of  organic  matter  in  the  water  increases  by 
sedimentation  from  above  and  by  solution  from  the  ooze  at 
the  bottom.  The  albuminoid  ammonia  increases.  Decom- 
position of  the  organic  matter  takes  place.  The  dissolved 
oxygen  disappears  and  the  nitrates,  iron,  etc.,  become 
reduced.  The  free  ammonia  and  nitrites  increase.  After 
the  supply  of  oxygen  has  become  exhausted,  putrefaction 
through  the  agency  of  the  anaerobic  bacteria  takes  place 
and  the  water  acquires  offensive  odors.  Increasing  amounts 
of  mineral  matter  are  taken  up  from  the  bottom  by  the  lower 
layers  of  water.  This  is  true  not  only  of  iron,  but  also  of 
silica,  manganese,  and  some  of  the  calcium  and  magnesium 
salts. 

These  stagnation  effects  are  observed  only  below  the 
thermocline.  The  relative  changes  that  occur  at  different 
depths  are  well  shown  by  the  amount  of  dissolved  oxygen, 
and  the  progress  of  the  changes  through  the  season  may  be 
studied  by  a  series  of  such  observations.  The  following 
tables  serve  to  illustrate  this:* 

DISSOLVED    OXYGEN    AT   VARIOUS    DEPTHS    IN    LAKE 
COCHITUATE,    IN    PER   CENT    OF   SATURATION. 


Surf 

10    f 
20 

30 
40 

45 
50 
56 

57^ 

Aug.  16,  1891. 

Sept.  28,  1891. 
90 
81 
33 
9 
8 

0 
0 

t               •                                  84 

•*6 

21 

2O 

o 

o 

*  Much  more  elaborate  studies  upon  this  subject  have  been  made  at 
Jamaica  Pond  by  the  Massachusetts  State  Board  of  Health.  For  further 
details  the  reader  is  referred  to  the  Special  Report  of  1890  on  Examination 
of  Water-supplies,  and  to  the  Annual  Reports  for  1891  and  1892. 


142  THE   MICROSCOPY  OF  DRINKING-WATER. 

FREE  CARBONIC  ACID  AT  VARIOUS  DEPTHS  IN  LAKE  COCHITUATE, 

(Parts  per  million.) 


Depth. 

May  24. 

IQOI 

Oct.  ir. 

1  901. 

Nov.  14, 

IQOI. 

Surface 

!-5 

4.0 

6.0 

1.0 

2.0 

3-° 

6.0 

.  20 

6.8 

IO.O 

6.0 

3° 

6.0 

II  .0 

6.0 

40 

10.  0 

II  .0 

6.0 

5° 

8.0 

19.0 

6.0 

60 

8.0 

23.0 

6.0  [52  ft.] 

The  effect  of  stagnation  upon  the  microscopic  organisms 
has  been  referred  to.  Little  life  exists  below  the  thermocline. 
The  ooze  at  the  bottom  is  largely  an  accumulation  of  dead 
organisms.  The  few  living  organisms  that  are  found  there 
are  Fungi,  Protozoa  and  Crustacea, — organisms  that  are 
parasitic  or  that  play  the  part  of  scavengers.  The  water  at 
the  bottom,  however,  acquires  a  supply  of  food-material — 
both  organic  and  mineral — suitable  for  microscopic  life.  After 
stagnation  ceases  and  the  period  of  circulation  begins,  this 
food-material  is  carried  to  the  upper  regions  where,  with 
light  and  oxygen,  the  organisms  are  able  to  utilize  it.  The 
diatoms  in  particular  depend  upon  the  food-supply  acquired 
by  the  water  during  periods  of  stagnation. 

The  stagnation  of  a  pond  that  has  deposits  of  organic 
matter  at  the  bottom  affects  the  quality  of  the  water  in  two 
ways.  When  the  bad  water  at  the  bottom  is  carried  to  the 
surface  during  the  periods  of  circulation  the  entire  body  of 
water  is  affected  by  it.  The  color  increases,  the  organic 
matter  increases,  and  the  odor  may  become  unpleasant. 
These  are  the  direct  effects.  Odors  of  the  water  that  are 
caused  by  the  growth  of  organisms  that  have  been  stimulated 
by  the  acquired  food-materials  are  the  indirect  effects. 


STORAGE   OF  SURFACE-WATER.  14* 

The  disagreeable  effects  of  stagnation  are  not  dependent 
upon  the  depth  of  a  pond,  except  in  so  far  as  the  depth 
affects  thermal  stratification.  They  depend  somewhat  upon 
the  character  of  the  water  stored,  but  much  more  upon  the 
amount  and  character  of  the  organic  matter  at  the  bottom  and 
upon  the  length  of  .the  stagnation  periods,  If  the  bottom  of 
the  reservoir  contains  no  organic  matter  the  phenomena 
described  above  will  not  occur.  It  has  been  found  that  in 
Basin  4  of  the  Boston  water-supply,  where  the  organic 
matter  was  carefully  removed  from  the  bottom,  the  dissolved 
oxygen  at  the  bottom  does  not  become  exhausted  during  the 
stagnation  periods,  although  it  is  appreciably  reduced  in 
amount.  The  author  once  collected  a  sample  from  Lake 
Champlain  at  a  depth  of  nearly  400  ft.  The  temperature 
was  39.2° — i.e.  maximum  density — and  the  water  was  prob- 
ably in  a  state  of  permanent  stagnation.  The  sample  was 
bright,  clear,  colorless,  and  without  odor.  The  material  on 
the  bottom  was  found  to  be  almost  perfectly  clean  gravel. 

Organic  matter  at  the  bottom  of  shallow  reservoirs  will 
cause  a  deterioration  of  the  water  stored  in  them.  If  there 
is  no  summer  stagnation  the  water  at  the  bottom  becomes 
warm,  and  decomposition  goes  on  rapidly.  The  products 
of  decay  taken  up  by  the  water  support  the  growth  of  organ- 
isms,— particularly  the  blue-green  algae.  Moreover,  during 
the  winter  when  the  surface  is  frozen  these  shallow  ponds 
grow  stagnant  and  the  conditions  become  similar  to  those 
in  deep  ponds.  After  the  periods  of  winter  stagnation, 
shallow  ponds  often  contain  heavy  growths  of  diatoms. 
Organic  matter  at  the  bottom  of  a  shallow  reservoir  affects 
the  quality  of  the  water  in  another  way.  It  offers  support 
for  fixed  aquatic  plants,  and  these  may  injure  the  quality  of  a 


144  THE   MICROSCOPY  OF  DRINKING-WATER. 

water  directly  by  their    decay   or  indirectly   by   harboring  the 
microscopic  organisms. 

The  evidence  is  conclusive  that  the  removal  of  the  organic 
matter  from  the  bottom  of  a  reservoir  is  an  important  factor 
in  the  prevention  of  the  growth  of  troublesome  organisms. 
To  what  extent  engineers  are  warranted  in  expending  large 
sums  of  money  for  the  cleaning  of  reservoir  sites  is  a  matter 
for  expert  opinion  in  every  individual  case.  The  removal  of 
trees,  stumps,  and  vegetation  is  always  wise.  The  removal 
of  the  upper  layers  of  soil  that  contain  large  percentages  of 
organic  matter  is  usually  advisable  but  not  always  necessary. 
In  lakes  of  the  first  order,  where  the  lower  layers  of  water  are 
in  a  state  of  permanent  stagnation,  the  character  of  the  bottom 
has  little  effect  upon  the  whole  body  of  water  because  the  lower 
layers  do  not  become  mixed  with  those  above.  In  artificial  reser- 
voirs, however,  this  condition  seldom  obtains,  and  the  character 
of  the  bottom  has  to  be  taken  into  consideration.  In  reservoirs 
designed  to  store  water  from  a  watershed  upon  which  there  are 
large  swamp  areas  and  where  the  water  entering  the  reservoir  is 
liable  to  contain  amounts  of  suspended  organic  matter  sufficient  to 
form  a  considerable  deposit  at  the  bottom,  it  may  not  be  wise  to 
remove  the  top  soil  to  any  great  depth,  because  in  the  course  of  a 
comparatively  few  years  the  effect  of  the  organic  matter  deposited 
by  the  water  may  equal  that  originally  present  in  the  soil.  Recent 
experience  has  shown  that  this  may  be  an  important  factor  even 
when  the  watershed  is  not  especially  swampy.  In  some  cases 
where  deposits  of  peat,  muck,  etc.,  extend  to  great  depth  it  may 
be  found  advisable  to  cover  the  surface  of  the  organic  matter 
with  clean  material  rather  than  to  excavate  it.  With  a  clean 
watershed,  however,  the  best  engineering  practice  endorses  the 
removal  of  the  top  soil  to  such  a  depth  that  the  upper  layer  of 
soil  remaining  shall  contain  not  more  than  about  2%  of  organic 


STORAGE  OF  SURFACE-WATER.  145 

matter,  as  determined  by  the  loss  on  ignition  of  a  sample  dried 
at  100°  C 

Wherever  possible,  deep  storage  reservoirs  should  be  so 
designed  that  the  lower  layers  of  water  may  be  drawn  off  and 
wasted  through  a  low-level  gate.  This  is  especially  important 
in  reservoirs  where  the  top  soil  has  not  been  removed.  It  is 
much  better  to  waste  the  bad  water  at  the  bottom  caused  by 
stagnation  than  to  allow  it  to  affect  the  entire  body  of  water 
in  the  reservoir. 

Experience  in  stripping  the  soil  from  reservoir  sites  appears  to 
indicate  that  this  practice  does  not  necessarily  insure  permanent 
freedom  from  the  presence  of  microscopic  organisms  in  the  stored 
waters.  Its  beneficial  effects  during  the  first  few  years  after  the  res- 
ervoir has  been  filled  are  usually  very  marked,  but  in  time  the  algae 
and  other  microscopic  organisms  are  likely  to  become  established. 
The  initial  benefits  derived  from  the  practice,  however,  may  be  suf- 
ficient to  warrant  its  expense.  Reservoirs  from  which  the  organic 
matter  is  not  removed  usually  cause  considerable  trouble  during 
the  first  few  years  after  construction,  but  this  gradually  dimin- 
ishes. It  thus  appears  that  with  time  a  reservoir,  whether  stripped 
of  its  organic  matter  or  not,  tends  to  approach  the  condition  of 
an  old  lake.  Whether  or  not  it  is  advisable  to  depend  upon  the 
stripping  of  the  reservoir  site,  or  upon  filtration,  as  a  means  of 
avoiding  bad  odors  due  to  algae,  is  a  matter  which  must  be  gov- 
erned by  the  particular  conditions  of  each  case.  Inasmuch, 
however,  as  filtration  is  becoming  necessary  for  sanitary  reasons 
this  method  of  maintaining  the  satisfactory  character  of  the 
water  appears  to  be  growing  in  favor. 

While  the  growth  of  algae  and  other  microscopic  organisms 
in  surface-waters  are  often  troublesome,  yet  at  times  they  tend 
to  improve  the  sanitary  quality  of  the  water.  The  following 
instances,  taken  from  the  records  of  Mt.  Prospect  Laboratory, 
illustrate  this: 


146 


THE  MICROSCOPY  OF  DRINKING-WATER. 


Baiseley's  Pond,  one  of  the  sources  of  water-supply  of  Brook- 
lyn, is  fed  by  a  number  of  streams  which  are  more  or  less  pol- 
luted. During  August,  1899,  the  water  of  the  pond  contained 
a  large  amount  of  Clathrocystis.  Bacteriological  examinations  of 
the  inflowing  streams  showed  that  the  water  contained*  from  1000 


FIG.  19— DIAGRAM  SHOWING  THE  NUMBER  OF  STANDARD  UNITS  OF  CLA- 
THROCYSTIS AND  THE  NUMBER  OF  BACTERIA  PER  CUBIC  CENTIMETER 
IN  THE  WATER  OF  BAISELEY'S  POND,  BROOKLYN  WATER  SUPPLY,  FOR 
EACH  MONTH  DURING  1898  AND  1899. 

to  17,000  bacteria  per  c.c.,  while  the  water  at  the  lower  end  of  the 
pond  contained  less  than  50  per  c.c.     A  study  of  the  analytical 


STORAGE   OF  SURFACE-WATER.  147 

records  for  the  same  pond  during  the  years  1898-9  showed  that 
the  number  of  bacteria  varied  inversely  with  the  number  of 
Clathrocystis.  (See  Fig.  19.) 

Laboratory  experiments  made  by  Strohmeyer  and  others 
corroborate  the  above  and  show  that  certain  algae  tend  to  reduce 
the  number  of  bacteria  in  water.  More  recent  experiments  by 
Emmerich  have  indicated  that  certain  protozoa  exercise  a  sim- 
ilar purifying  effect  on  surface-waters.  He  has  found  that  two 
species  of  the  genus  Bodo  will  very  greatly  reduce  the  number 
of  typhoid-fever  germs  in  water.  Staining  of  the  organisms  shows 
that  the  bacteria  are  absorbed  by  the  animal-cell,  the  action 
being  analogous  to  that  of  the  white-blood  corpuscles  in  the 
human  body  upon  which  Metchnikoff's  theory  of  phagocytosis 
was  based.  Emmerich  considers  that  these  and  other  protozoa 
play  an  important  part  in  the  self-purification  of  streams. 


CHAPTER    XI. 
STORAGE   OF  GROUND-WATER. 

Ground-water  must  be  stored  in  the  dark  in  order  to  pre~ 
vent  the  growth  of  microscopic  organisms. 

Water  that  has  passed  through  the  soil  usually  carries 
much  mineral  matter  in  solution,  some  of  which  forms  an 
important  ingredient  of  plant-food.  When  such  water  is 
stored  in  an  open  reservoir  it  is  liable  to  deteriorate.  Diatoms 
especially  are  liable  to  develop,  because  their  mineral  contents 
are  greater  than  those  of  most  plants.  These  growths  are 
less  likely  to  occur  in  a  new  reservoir  than  in  one  that  has 
been  long  in  use.  The  seeding  of  the  reservoir  must  first 
take  place.  As  a  rule  some  of  the  littoral  organisms 
develop  first,  growing  on  the  sides  or  even  on  the  bottom  of 
the  reservoir.  Gradually  a  deposit  of  organic  matter  collects 
at  the  bottom,  and  the  conditions  become  favorable  for  the 
growth  of  the  limnetic  organisms. 

Of  the  diatoms  that  occur  in  ground-water  exposed  to  the 
light  Asterionella  is  by  far  the  most  troublesome.  Others 
may  make  the  water  turbid,  but  the  Asterionella  is  very 
odoriferous.  In  surface-waters  it  has  been  found  that  this  or- 
ganism develops  most  vigorously  after  the  stagnation  periods. 
It  is  probable  that  this  is  true  also  in  ground-waters.  Most 
reservoirs  for  the  storage  of  ground-water  are  shallow  and  of 
comparatively  small  size.  Often  water  is  not  pumped 
directly  through  them.  Such  reservoirs  become  stagnant  at 

148 


STORAGE    OF  GROUND-WATER.  149 

times,  and  it  has  been  observed  that  in  them  the  Asterionella 
show  a  spring  and  fall  seasonal  distribution  like  that  observed 
in  surface-waters.  It  sometimes  happens  that  for  many  years 
an  open  reservoir  gives  no  trouble,  but  that  finally  a  layer  of 
organic  matter  accumulates  at  the  bottom,  the  water  in  some 
way  becomes  seeded  with  Asterionella,  and  thereafter  regular 
growths  of  these  organisms  occur.  If  open  reservoirs  are  to 
be  used  for  the  storage  of  ground-water  they  should  be  kept 
clean. 

When  a  water-supply  is  taken  partly  from  the  surface  and 
partly  from  the  ground  it  is  even  more  necessary  that  covered 
storage  reservoirs  should  be  used,  because  the  surface-water 
may  contain  organisms  the  growth  of  which  in  the  reservoir 
may  be  stimulated  by  the  food-material  in  the  ground-water, 
and  because  organic  matter  will  be  deposited  from  the  sur- 
face-water, increasing  the  effects  of  stagnation  and  making 
it  possible  for  Asterionella  growths  to  occur.  The  water- 
supply  of  Brooklyn,  N.  Y.,  presents  an  interesting  example. 

The  supply  of  this  city  is  derived  from  a  number  of  small 
storage  reservoirs  along  the  southern  shore  of  Long  Island  and 
from  fourteen  driven-well  stations  along  the  line  of  the  aque- 
duct. The  well-water  is  drawn  from  depths  varying  between 
25  and  200  ft.  The  waters  become  mixed  in  the  aqueduct 
and  are  stored  in  three  basins  comprising  Ridgewood  Reser- 
voir. The  different  sources  of  water  vary  greatly  in  character. 
Some  contain  an  abundance  of  organic  matter;  some  have 
high  free  ammonia,  nitrites,  and  nitrates;  some  have  consider- 
able iron;  and  one  or  two  have  high  chlorine  and  hardness 
due  to  admixture  of  a  small  amount  of  sea-water.  The 
watershed  is  sandy,  and  all  the  waters  are  rich  in  silica. 

In  1896  Asterionella  developed  in  Ridgewood  Reservoir 
in  great  abundance,  and  since  then  it  has  reappeared  at  inter- 


THE   MICROSCOPY  OF  DRINKING-WATER. 

vals.  In  a  general  way  these  growths  have  shown  the  spring 
and  fall  distribution,  but  they  also  correspond  to  some  extent 
with  increased  proportions  of  ground-water  used.  At  times  the 
numbers  of  Asterionella  present  have  been  very  high, — 25  ooo 
r,r  30000  per  c.c.  For  many  years  Ridgewood  Reservoir  caused 
no  trouble  and  the  water-supply  bore  an  enviable  reputation. 
H  was  not  until  a  considerable  deposit  of  diatoms  and  other 
organic  matter  had  accumulated  on  the  bottom  of  the  basins  and 
until  the  amount  of  ground- water  had  come  to  be  about  40% 
of  the  total  supply  that  the  conditions  became  favorable  for  such 
enormous  growths  of  Asterionella.  Fortunately  for  the  con- 
sumers, a  by-pass  around  the  distributing-reservoir  permits  the 
water  to  be  pumped  from  the  aqueduct  directly  into  the  dis- 
tribution system.  This  is  used  whenever  the  Asterionella  in 
the  reservoir  become  abundant  enough  to  cause  a  bad  odor. 

Water  that  has  been  filtered  resembles  ground- water,  and 
microscopic  organisms  may  develop  in  it  to  such  an  extent  as 
to  cause  trouble.  For  this  reason  provision  is  generally  made 
for  storing  filtered  water  in  covered  reservoirs.  Often,  how- 
ever, from  motives  of  economy,  it  is  necessary  to  use  existing 
reservoirs  which  are  not  covered.  Such  reservoirs  at  times 
become  affected  with  microscopic  organisms,  but  these  seldom 
cause  as  much  trouble  in  filtered  water  as  in  ground-water  exposed 
under  similar  conditions.  Water  which  has  been  filtered  by  the 
mechanical.system  of  filtration  is  somewhat  more  liable  to  growths 
than  the  same  water  filtered  by  sand  filtration.  This  is  because 
the  use  of  alum  leaves  a  certain  amount  of  dissolved  free  carbonic 
acid  in  the  water,  which  tends  to  favor  the  growth  of  the  organisms. 
On  the  other  hand  the  effluent  of  a  sand  filter  may  contain  a 
larger  amount  of  nitrogen  in  the  form  of  nitrate,  a  condition  in 
which  it  is  more  available  for  use  by  the  algae.  The  controlling 
factor,  however,  is  usually  the  length  of  storage  in  the  reservoir* 


STORAGE   OF   GROUND-WATER. 


If  the  period  is  short  the  growths  are  usually  insignificant,  -but 
if  the  water  is  kept  in  the  reservoir  for  many  days  algae  are 
likely  to  develop  to  a  troublesome  extent. 

As  an  illustration  of  the  effect  of  storage  on  a  filtered  water  the 
following  figures  taken  from  analyses  of  the  Hudson  River  water  at 
Poughkeepsie,  New  York,  before  and  after  filtration  are  interesting: 


/        Date,  1903. 

Microscopic  Organisms 
per  c.c. 

Raw  Water. 

Filtered 
Water  after 
Storage. 

April  23  

60 
70 
95 
65 
205 
230 
185 

1455 

'35 

65 
130 

655 

2440 

2265 

May  1  1 

June  8 

June  20        

Tulv  8 

jury  o.  ... 

Tulv  2  3  

Darkness  is  not  always  sufficient  to  prevent  a  ground- water 
from  deteriorating.  There  are  some  organisms  that  can  live 
without  light,  and  indeed  prefer  darkness.  Of  such  a  nature  are 
the  fungi  (using  the  word  in  its  broad  sense  as  including  those  vege- 
table forms  destitute  of  chlorophyll)  and  some  of  the  protozoa. 

Crenothrix  is  the  most  important  organism  of  this  character 
that  affects  ground-water  supplies.  It  is  a  small  filamentous 
plant,  the  cells  of  which  are  but  little  larger  than  the  bacteria. 
Its  filaments  have  a  gelatinous  sheath  colored  brown  by  a  deposit 
of  ferric  oxide.  It  grows  in  tufts,  sometimes  matted  together  into 
a  felt-like  layer. 

Crenothrix  is  liable  to  occur  in  ground- water  rich  in  iron  and 
organic  matter.  It  frequently  infests  water  obtained  from  wells 
driven  in  swampy  land.  It  is  often  observed  in  imperfectly 
filtered  water.  It  may  grow  in  almost  any  part  of  the  system, — 
in  the  driven  wells,  filter-galleries,  reservoirs,  and  distribution- 
pipes.  It  is  especially  liable  to  occur  about  woodwork. 

Crenothrix  causes  trouble  in  tubular  wells  by  choking  them 


152  THE   MICROSCOPY   OF  DRINKING-WATER. 

• 

with  deposits  of  iron.  Leptothrix,  Spirochaetae,  and  allied  organ- 
isms also  do  this.  Crenothrix  causes  trouble  in  the  service-pipes 
by  reducing  the  capacity  of  the  pipe.  But  it  causes  most  trouble 
when  the  filaments  break  off  and  become  scattered  through  the 
water.  It  is  then  liable  to  make  the  water  unfit  for  laundry  use 
on  account  of  deposits  of  iron-rust. 

Crenothrix  has  caused  annoyance  in  many  water-supplies. 
The  "water  calamity"  in  Berlin  first  drew  attention  to  its  evil 
effects.  In  1878  the  water  from  the  Tegel  supply  became  filled 
with  small,  yellowish-brown,  flocculent  masses  which  settled 
to  the  bottom  when  the  water  was  allowed  to  stand  in  a  jar. 
The  odor  of  the  water  and  the  effects  of  the  iron  oxide  in  wash- 
ing were  decidedly  troublesome.  Crenothrix  was  not  found  in 
Lake  Tegel,  but  was  found  in  many  wells,  in  the  reservoirs  at 
Charlottenburg  and  in  the  unfiltered  water  of  the  river  Spree. 

In  1887  the  water-supply  of  Rotterdam  was  badly  affected 
with  Crenothrix.  The  water  was  drawn  from  the  river  Maas, 
and,  after  sedimentation,  was  filtered.  At  the  time  when  Creno- 
thrix appeared  the  system  was  being  enlarged.  New  filter-beds 
were  in  use,  but  the  filtered  water  was  conducted  through  the 
old  conduits  and  the  old  reservoir  to  the  old  pumps.  In  the 
old  conduit,  or  flume,  there  were  many  wooden  timbers,  and  on 
these  Crenothrix  was  found  growing  in  abundance.  Inspection 
showed  that  some  of  the  water  was  imperfectly  filtered,  and 
that  this  impure  water  was  the  chief  cause  of  the  sudden  and 
extensive  development  of  Crenothrix. 

It  has  been  recently  found  that  Crenothrix  thrives  best  in  water 
which  contains  little  or  no  oxygen  but  where  carbonic  oxygen 
is  present  in  considerable  amounts.  Mr.  D.  D.  Jackson  has 
described  three  species  of  Crenothrix,  one  of  which  deposits  iron 
in  its  sheath,  another  manganese,  and  another  alumina.  The 
second  of  these  is  a  new  species,  the  third  is  the  well-known. 
Leptothrix  ochracea. 


CHAPTER  XII. 

METHODS   OF   TREATING    WATERS    WHICH   CONTAIN 
MICROSCOPIC    ORGANISMS. 

VARIOUS  methods  have  been  suggested  from  time  to  time  for 
treating  waters  which  are  obnoxious  by  reason  of  the  growths  of 
microscopic  organisms.  A  number  of  years  ago  aeration  was 
considered  as  a  remedy.  The  reservoirs  of  the  Hackensack  Water 
Company,  in  New  Jersey,  were  supplied  with  pipes  through  which 
air  was  blown  into  the  water.  This  was  thought  at  the  time  to 
have  produced  beneficial  results,  but  the  method  has  not  stood 
the  test  of  further  experience.  Aeration  of  water  brought  about 
by  exposing  it  in  thin  films  to  the  air  produces  conditions  which 
tend  not  only  to  decrease  the  growth  of  microscopic  organisms 
but  to  remove  their  objectionable  products.  This  is  due,  however, 
not  so  much  to  the  increase  of  the  oxygen-content  of  the  water  as 
to  the  reduction  of  free  carbonic  acid  by  exposure  to  the  atmos- 
phere and  to  a  similar  loss  of  the  odoriferous  substances.  When 
water  is  allowed  to  flow  down  a  running  brook  over  stones  which 
produce  ripples  and  waterfalls  the  microscopic  organisms  may 
become  disintegrated  and  their  odoriferous  constituents  may 
diffuse  into  the  atmosphere,  and  this  may  cause  a  decided  im- 
provement in  the  quality  of  the  water.  A  similar  disintegration 
of  the  organisms  may  take  place  in  the  pipes  of  a  distribution 
system,  but  in  this  case  there  is  no  chance  for  the  odoriferous  sub- 
stances to  be  lost,  and  the  disintegration  of  the  organisms,  there- 
fore, may  only  intensify  the  odor  of  the  water. 

153 


I  54  THE  MICRO  SCOP  Y  OF  DRINKING-  WA  TER. 

It  often  happens  that  a  water- works  system  is  so  arranged 
that  the  reservoir  can  be  cut  out  of  service  if  the  water  in  it  be- 
comes affected  with  growths  of  algae.  When  a  reservoir  is  thus 
allowed  to  remain  standing  the  organisms  sometimes  disappear 
in  the  course  of  a  short  time.  This  cannot  always  be  depended 
upon,  however.  Reservoirs  thus  isolated  sometimes  remain  in  a 
foul  condition  for  many  months.  In  case  an  open  reservoir  is 
used  for  the  storage  of  ground-water,  however,  it  should  be 
provided  with  a  by-pass  in  order  that  this  method  of  isolation 
may  be  resorted  to  in  case  of  need. 

The  use  of  house  filters  at  the  tap  for  removing  microscopic 
organisms  is  quite  common.  Some  of  these  filters  give  reasonably 
satisfactory  results  if  properly  cared  for,  but  generally  their  use 
is  not  to  be  recommended  for  sanitary  reasons.  Porcelain  or 
stone  filters,  such  as  the  Pasteur  Filter  and  the  Berkefeld 
Filter,  remove  the  microscopic  organisms  completely,  but  they 
do  not  remove  all  of  the  odors  produced  by  them.  They 
also  improve  the  sanitary  quality  of  the  water,  but  they  clog 
rapidly  and  yield  but  little  water.  Charcoal  filters  remove  the 
odor  as  well  as  the  organisms,  but  for  sanitary  reasons  they  are 
more  objectionable  than  the  other  types.  In  certain  cases  the 
use  of  sand  and  charcoal  with  liberal  aeration  of  the  water  gives 
reasonably  satisfactory  results.  In  general,  however,  methods  of 
house  filtration  prove  expensive  and  disappointing. 

When  the  number  of  microscopic  organisms  in  water  is  not 
large,  slow-sand  filtration  or  mechanical  filtration  offers  the  best 
modes  of  treatment  of  algae-laden  waters.  When  present  in  very 
large  numbers  filtration  becomes  difficult  and  expensive.  If 
mechanical  filters  are  used  the  organisms  quickly  clog  the  sand- 
beds  and  this  necessitates  frequent  washing  of  the  filters  and  the 
use  of  large  amounts  of  wash-water.  Furthermore,  the  odors 
due  to  the  organisms  are  not  removed  by  such  filtration,  and 


ME  THODS   OF    7  RE  A  7  MENT.  1 5  5 

aeration  may  be  required  as  a  supplementary  process.  There 
are  instances  on  record  where  mechanical  filters  have  been  almost 
completely  stopped  by  reason  of  growths  of  diatoms  and  other 
organisms.  Diatoms  in  particular  cause  trouble  in  the  washing 
of  mechanical  filters,  because  their  hydraulic  subsiding  value  is 
more  nearly  like  that  of  the  sand-grains  than  is  the  case  with 
other  organisms. 

Sand  filtration  is  generally  more  applicable  to  the  treatment 
of  waters  which  contain  microscopic  organisms  than  is  mechani- 
cal filtration.  This  is  partly  because  a  much  lower  rate  of  filtra- 
tion is  used.  In  the  case  of  open  sand  filters  the  film  on  the 
top  of  the  sand  often  contains  microscopic  organisms  in  large 
numbers,  even  when  these  are  not  abundant  in  the  raw  water, — 
that  is,  the  organisms  grow  on  the  sand.  The  following  is  an 
illustration  of  this:  An  experimental  sand  filter  at  the  Chestnut 
Hill  Reservoir,  Boston,  became  so  clogged  after  running  for  25 
days  that  it  was  necessary  to  scrape  the  surface  of  the  sand. 
Microscopical  examinations  showed  that  over  each  square  centi- 
meter there  were  2  500  ooo  Tabellaria  and  i  ooo  ooo  Synedra, 
besides  many  other  microscopic  organisms.  Calculations  from 
the  analyses,  of  the  raw  water  showed  that  during  the  25  days 
when  the  filter  had  been  in  operation  only  150000  Tabellaria 
and  20  ooo  Synedra  were  removed  from  the  water  by  each  square 
centimeter  of  the  filter.  The  difference  between  the  two  sets  of 
figures  represents  the  growth  of  organisms  upon  the  sand. 
Samples  of  scum  taken  from  various  filters  in  practical  opera- 
tion have  shown  the  presence  of  microscopic  organisms  in  num- 
bers which  range  from  a  few  thousand  to  several  million  per 
square  centimeter  of  surface  area.  The  presence  of  these  organ- 
isms aids  filtration  in  a  certain  sense  by  forming  a  tenacious 
surface-scum  over  the  sand.  This  schmutzdecke,  however, 
forms  even  without  their  presence,  and  accumulations  of  organ- 


1 56  THE  MICROSCOP  Y  OF  DRINKING-  WA  1  ER. 

isms  above  the  sand  are,  on  the  whole,  likely  to  do  more  harm 
than  good.  They  cause  the  filter  to  clog  more  quickly  than  it 
otherwise  would,  and,  therefore,  increase  the  cost  of  operation. 
Furthermore,  when  open  niters  are  used  these  algae  growths 
sometimes  interfere  with  filtration  in  another  way.  When  their 
growth  is  vigorous  the  amount  of  gas  liberated  from  them  some- 
times becomes  so  great  that  masses  of  the  organisms  are  lifted 
from  the  sand  layer  and  floated  to  the  surface.  Spots  of  sand 
are,  therefore,  left  uncovered,  and  the  water  filters  through  them 
more  rapidly  than  it  should,  with  the  result  that  filtration  is 
imperfect.  When  filters  are  covered  with  roofs  these  organisms 
do  not  grow  on  the  sand  surface  and  those  which  are  found  there 
represent  accumulations  from  the  raw  water. 

Sand  filtration  will  usually  reduce  the  odor  of  algae-laden 
water,  but  it  will  not  always  remove  it  completely.  Sometimes  it 
fails  utterly.  This  is  particularly  true  when  Anaebena  and  other 
blue-green  algae  are  present  in  large  numbers.  Sand  filtration, 
accompanied  by  aeration,  usually  results  in  giving  a  satisfactory 
degree  of  purification,  but  in  extreme  cases  it  may  be  necessary  to 
resort  to  a  double  system  of  nitration,  supplemented  by  prelim- 
inary and  final  aeration. 

An  interesting  case,  which  shows  the  difficulty  of  filtering  water 
which  contains  algae,  is  that  of  the  Ludlow  Supply  of  Springfield, 
Mass.,  which  during  the  last  few  years  has  been  studied  experi- 
mentally by  the  city  and  by  the  Massachusetts  State  Board 
of  Health. 

Ludlow  Reservoir  is  about  400  acres  in  extent  and  about  n 
feet  deep  on  an  average,  its  maximum  depth  being  20  feet.  Its 
bottom  is  almost  entirely  covered  with  a  layer  of  mud  many  feet 
in  thickness.  For  many  years  the  water  each  summer  has  been 
rendered  foul  by  enormous  growths  of  Anaebena.  At  times 
more  than  20000  standard  units  of  this  organism  have  been 


METHODS   OF   TREATMENT.  I  57 

present  in  each  cubic  centimeter  of  the  water,  and  the  odor  of 
it  has  been  noxious  in  the  extreme.  The  water  often  has  been 
practically  undrinkable.  The  experiments  showed  that  single 
sand  filtration  would  not  purify  the  water  satisfactorily  during 
the  summer  season,  and  in  order  to  render  it  satisfactory  it 
would  be  necessary  to  filter  the  water  twice  and  to  aerate  it 
before  and  after  each  filtration.  The  object  of  the  preliminary 
aeration  was  to  supply  oxygen,  which  the  raw  water  lacked 
when  Anaebena  growths  were  present.  The  object  of  the  final 
aeration  was  to  eliminate  the  odoriferous  substances  from  the 
water  which  were  not  entirely  removed  by  the  filters. 

A  new  method  of  treating  water-supplies  which  contain 
algse  or  other  microscopic  organisms  was  recently  suggested  by 
Dr.  Geo.  T.  Moore  and  Mr.  Karl  F.  Kellerman,  of  the  U.  S. 
Department  of  Agriculture.  It  consists  of  using  sulphate  of  cop- 
per, or  blue  vitriol,  a  substance  which  possesses  powerful  toxic 
properties  for  these  organisms.  The  use  of  copper  as  a  fungi- 
cide has  been  practiced  for  a  long  time,  and  it  has  been  a  matter 
of  common  knowledge  to  botanists  and  bacteriologists  that 
copper  salts  have  a  high  degree  of  toxicity  for  the  lower  forms 
of  life,  and  especially  for  the  unicellular  organisms.  To  Dr. 
Moore,  however,  belongs  the  credit  of  demonstrating  the  practi- 
cal applicability  of  this  chemical  to  the  clarification  of  large 
bodies  of  water  containing  algae. 

His  method  of  application  consists  of  putting  the  requisite 
quantity  of  the  chemical  into  a  coarse  bag,  or  gunny  sack,  and 
drawing  it  slowly  back  and  forth  over  the  reservoir  attached  to 
the  stern  of  a  boat,  thus  relying  upon  diffusion  and  the  natural 
circulation  of  the  water  to  mix  the  chemical.  Dr.  Moore  cal- 
culated that  in  this  way  about  100  pounds  of  copper  sulphate 
•could  be  dissolved  in  one  hour. 

The  amount  of  copper  sulphate  necessary  to  be  applied  to 


158  THE  MICROSCOPY  OF  DRINKING-WATER. 

kill  the  algae  varies  according  to  the  organisms  present,  the  tem- 
perature of  the  water,  the  amount  of  dissolved  organic  matter, 
the  hardness  of  the  water,  and  other  factors.  In  the  case  of  the 
more  fragile  organisms,  such  as  Uroglena  and  Anaebena,  dilutions 
of  one  part  of  copper  sulphate  to  5  or  20  million  parts  of  water  by 
weight  suffice;  while  in  the  case  of  the  more  hardy  organisms, 
such  as  the  diatoms,  the  amounts  required  may  be  as  great  as 
one  part  in  one  million  or  even  greater.  Fortunately,  however, 
the  organisms  which  are  the  most  troublesome  are  the  ones  most 
easily  killed. 

The  copper  treatment  has  been  used  in  many  reservoirs  on  a 
large  scale,  and  has  apparently  met  with  a  considerable  degree 
of  success.  In  some  cases,  however,  it  is  said  not  to  have  given 
entire  satisfaction,  the  disappearance  of  one  organism  being 
immediately  followed  by  trie  growth  of  other  and  more  objection- 
able forms. 

The  chief  objection  which  has  been  raised  against  this  method 
has  been  the  poisonous  character  of  the  substance  used.  There 
is  little  reason,  however,  to  believe  that  much  is  to  be  feared 
from  the  occasional  use  of  sulphate  of  copper  in  very  dilute 
solutions.  This  matter  is  one  upon  which  little  is  known,  and 
upon  which  more*  precise  physiological  data  are  much  needed. 
It  is  claimed  that  much  of  the  copper  which  is  used  disappears 
from  the  water  after  treatment,  some  of  it  combining  with  organic 
matter  and  some  of  it  being  precipitated  as  an  insoluble  basic 
carbonate.  Recent  observations  indicate,  however,  that  this 
claim  is  not  fully  substantiated  and  that  nearly  all  of  the  copper 
introduced  into  a  reservoir  must  be  sooner  or  later  dissolved  in 
the  water  or  carried  into  suspension,  so  that  practically  all  of  it 
will  ultimately  reach  the  consumers.  It  may  even  happen  that 
some  portions  of  the  water  become  more  highly  charged  with 
copper  than  the  calculated  dilution  would  indicate.  In  cases 


METHODS   OF   TREATMENT.  159 

where  the  use  of  copper  sulphate  is  followed  by  filtration  of 
the  water  the  salt  is  very  largely  removed  and  little  is  to  be 
feared  from  its  use. 

At  this  date  (March,  1905)  there  are  many  problems  connected 
with  the  use  of  copper  as  an  algicide  which  need  further  study. 
From  what  is  now  known  its  use  as  an  emergency  measure 
in  the  treatment  of  water-supplies  affected  with  algae  growths 
appears  to  be  most  promising.  Its  constant  use  must  be  looked 
upon  at  present  as  one  of  doubtful  expediency  until  more  is 
known  about  the  physiological  action  of  minute  traces  of  copper. 
The  promiscuous  use  of  copper  by  those  who  have  no  knowl- 
edge of  chemistry,  or  of  the  physical  laws  which  govern  the 
circulation  of  large  bodies  of  water,  should  be  emphatically 
condemned. 


CHAPTER  XIII. 


GROWTH   OF  ORGANISMS   IN   WATER-PIPES. 

THE  reactions  between  the  water  and  the  water-pipes  of 
a  water-works  system  involve  such  matters  as  iron-rusting, 
tuberculations,  lead-poisoning,  and  others  of  a  chemical  and 
physical  nature.  There  are  also  biological  reactions.  These 
may  be  considered  under  two  heads:  (i)  the  effect  of  the 
aqueducts  and  pipes  upon  the  biology  of  the  water,  and  (2) 
the  effect  of  the  water  upon  the  biology  of  the  aqueducts  and 


pipes. 


I.   The  temperature  of  water  changes  during  its  passage 


70° 

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TEMPERATURE  OF      v\ 
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AVERAGE  OF  WEEKLY 
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through  the  pipes  of  a  distribution  system.     The  nature  of 
these  changes  is  shown  by  Fig.  20,  where  the  curves  represent 

160 


GROWTH  OF  ORGANISMS  IN    WATER-PIPES.  l6l 

the  averages  of  weekly  temperature  observations  for  five  years 
at  Chestnut  Hill  Reservoir  and  at  two  taps,  one  at  Park 
Square,  5  miles  from  the  reservoir,  and  the  other  at  Mattapan, 
1 1  miles  from  the  reservoir.  During  the  spring  and  summer 
the  water  grows  cooler  as  it  passes  through  the  pipes,  and  dur- 
ing the  autumn  and  winter  it  grows  warmer.  The  maximum 
temperature  at  Mattapan  is  never  as  high  as  that  at  Park 
Square,  but  the  minimum  temperature  is  about  the  same  at 
both  places,  though  it  occurs  later  in  the  season  at  Mattapan. 
Samples  taken  at  the  same  places  serve  to  illustrate  the 
changes  that  take  place  in  the  organisms  of  the  water  due  to 
their  passage  through  the  pipes.  Weekly  observations  for 
five  years  (1891-5)  showed  the  following  average  number  of 
organisms  present: 

Number  of  Standard  Units  per  c.c. 
Organisms.  Amorphous  Matter. 

Chestnut  Hill  Reservoir 248  222 

Brookline  Reservoir 215  212 

Tap  in  Park  Square 189  190 

Tap  in  Mattapan 81  105 

The  greatest  reduction  does  not  occur  near  the  reservoirs, 
where  the  pipes  are  large  and  the  currents  swift,  but  at  the 
extremities  of  the  distribution  system,  where  the  pipes  are 
smaller. 

The  observations  showed  that  during  the  winter,  when 
there  are  comparatively  few  organisms  in  the  water,  the 
reduction  in  the  pipes  is  much  less  than  during  the  summer, 
when  organisms  are  more  abundant.  During  the  six  months 
of  the  year,  from  November  to  April,  there  was  a  reduc- 
tion of  44$  in  organisms  and  24$  in  amorphous  matter  in 
about  6  miles  of  pipe;  while  during  the  six  months  from 
May  to  October  the  reduction  was  62$  for  the  organisms 
and  53$  for  the  amorphous  matter.  It  is  worth  noting  that 


162 


THE   MICROSCOP  Y   OF  DRINKING-  WA  TER. 


the  reduction  in   organisms  was  greater  than  the  reduction  in 
amorphous  matter. 

Not  only  are  the  microscopic  organisms  and  amorphous 
matter  reduced  in  the  pipes,  but  the  bacteria  also  tend  to 
decrease.  This  fact  has  been  observed  in  many  cities.  In 
the  pipes  of  the  Boston  Water  Works  the  decrease  does  not 
occur  throughout  the  entire  year.  In  the  summer,  when  the 
temperature  of  the  water  is  high  and  when  the  organisms  in 
the  water  and  those  growing  in  the  pipes  are  passing  rapidly 
through  stages  of  growth  and  decay,  there  is  a  considerable 
increase.  This  is  shown  in  Fig.  21. 


MICROSCOPIC  ORGANISMS,  BACTERIA.AND  AMORPHOUS  MATTER 
IN  THE  BOSTON  WATER  PIPES.   THE  CURVES  REPRESENT  THE 
AVERAGES  OF  WEEKLY  ANALYSES  FOR  THE  YEARS  1891-5. 

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In  order  to  determine  what  organisms  showed  the  greatest 
reduction  in  the  pipes,  a  detailed  study  of  the  examinations 


GROWTH   OF  ORGANISMS   IN    WATER-PIPES.  163 

above   referred   to   was   made    for  the  years   1892   and    1893. 
The  following  were  the  results: 

PERCENTAGE  REDUCTION  OF  MICROSCOPIC  ORGANISMS  IN 
THE  DISTRIBUTION-PIPES  BETWEEN  PARK  SQUARE  AND 
MATTAPAN,  BOSTON,  MASS. 

Average  for  the  years 

1892  and  1893. 

Diatomaceae 58  per  cent 

Chlorophyceae 57    "       " 

Cyanophyceae 54    * '       " 

Protozoa 64    "       " 

Miscellaneous 58    "      " 

Organisms  of  all  kinds 56    "       " 

Questions  naturally  arise  as  to  the  cause  and  effect  of  this 
reduction  of  organisms  in  the  pipes.  They  may  be  considered 
under  the  following  topics:  sedimentation,  disintegration, 
decomposition,  and  consumption  by  other  organisms. 

Most  of  the  microscopic  organisms  are  heavier  than  water. 
Some  always  settle  in  quiet  water,  and  they  do  so  in  the 
pipes  whenever  the  current  is  reduced  to  a  certain  point. 
Others,  which  in  ponds  usually  rise  to  the  surface  on  account 
of  the  gas-bubbles  which  they  contain,  will  settle  in  the  pipes 
when  the  pressure  of  the  water  has  deprived  them  of  their  gas. 
In  dead  ends  the  organisms  and  particles  of  amorphous  matter 
often  accumulate  and  form  deposits  upon  the  bottom  of  the 
pipes.  They  also  tend  to  deposit  on  up-grades.  It  is  a 
matter  of  frequent  observation  that  the  water  from  the  high 
points  of  a  distribution  system  contains  fewer  organisms  than 
that  from  the  low  points.  The  same  fact  has  been  observed 
in  high  buildings,  where  the  difference  between  the  water  on 
the  upper  stories  and  that  on  the  lower  floor  is  often  con- 
siderable. 


164  THE   MICROSCOPY  OF  DRINKING-WATER. 

Many  of  the  common  organisms  are  very  fragile.  Even 
a  slight  agitation  of  the  water  will  break  them  up.  This  is 
particularly  true  of  certain  Protozoa,  but  it  also  happens  to 
the  siliceous  cells  of  diatoms. 

The  organisms  found  in  surface-waters  are  accustomed  to 
live  in  the  light.  When  they  enter  the  dark  pipes  they  are 
liable  to  die  and  decompose.  This  is  particularly  true  of 
some  of  the  organisms  that  are  abundant  in  the  summer. 
Microscopical  examination  of  samples  from  the  service-taps 
has  often  revealed  organisms  in  a  decomposing  condition, 
swarming  with  bacteria.  This  decomposition  tends  to  reduce 
the  numbers  of  organisms  in  the  pipes. 

Another  important  consideration  in  the  reduction  of 
organisms  is  the  fact  that  in  many  of  the  distribution  systems 
where  surface-waters  are  used  the  pipes  are  covered  with 
growths  of  sponge,  etc.  These  attached  growths  depend  for 
their  food-material  upon  the  minute  organisms  found  in  the 
water.  If  the  growths  are  abundant,  the  removal  of  organ- 
isms from  the  water  by  this  means  may  be  considerable. 

2.  Comparatively  little  has  been  written  in  this  country 
upon  the  biology  of  aqueducts  and  pipes.  Our  attention  has 
been  called  to  growths  of  Crenothrix  and  of  fresh-water 
sponge,  but  no  attempt  has  been  made  to  give  an  accurate 
account  of  the  organisms  infesting  the  distribution  systems  of 
our  water-supplies.  In  Europe,  however,  the  subject  has 
been  considered  to  some  extent. 

In  the  city  of  Hamburg  the  minute  animals  inhabiting 
water-pipes  were  studied  by  Hartwig  Petersen  in  1876.  Ten 
years  later  Karl  Kraepelin  made  a  more  extended  study. 
His  observations  were  of  much  interest.  He  found  an  animal 
growth,  often  more  than  one  centimeter  thick,  covering  the 
entire  surface  of  the  pipes.  The  composition  of  this  growth 


GROWTH  OF  ORGANISMS  IN    WATER-PIPES.  165 

varied  in  different  places.  He  gave  a  list  of  sixty  different 
species  observed.  In  many  places  the  walls  of  the  pipes  were 
covered  with  fresh-water  sponges,  chiefly  Spongilla  fluviatilis 
and  Spongilla  lacustris.  Mollusks  were  conspicuous,  espe- 
cially the  mussel,  Dreyssena  polymorpha.  Snails  were  also 
numerous.  Hundreds  of  "  water-lice  "  (Asellus  aquaticus) 
and  "water-crabs"  (Gammarus  pulex)  were  found  at  every 
examination.  The  material  known  as  "pipe-moss  "  was  com- 
mon, and  consisted  largely  of  Cordylophora  lacustris  and  the 
Bryozoa,  Plumatella  and  Paludicella. 

At  the  time  when  Crenothrix  was  giving  so  much  trouble 
at  Rotterdam,  Hugo  de  Vries  made  an  extended  study  of  the 
animals  and  plants  found  in  the  water-pipes  of  that  city. 
His  observations  were  confined  chiefly  to  the  pipes  and  canals 
which  conveyed  the  unfiltered  water  of  the  river  Maas  to  the 
filter-beds.  In  speaking  of  one  of  the  canals  he  said:  "  The 
walls  were  thickly  covered  with  living  organisms  up  to  the 
water-level.  They  formed  an  almost  continuous  coating  of 
varying  composition.  There  were  only  one  or  two  excep- 
tions to  this.  In  one  place,  where  the  water  came  from  the 
pumps  with  great  velocity,  the  walls  were  free  from  living 
organisms;  and  in  another  place,  where  there  was  almost  no 
current,  only  one  living  form  was  seen.  There  was  a  sec- 
tion of  one  of  the  canals,  where  a  gentle  current  was  flowing, 
that  was  a  magnificent  aquarium.  The  walls  were  everywhere 
covered  with  white  tufts  of  fresh-water  sponge  (Spongilla 
fluviatilis).  Many  of  these  tufts  reached  a  diameter  of  6 
or  8  inches,  but  most  of  them  were  somewhat  smaller. 
Between  the  sponge  patches  were  seated  countless  numbers 
of  the  mussel,  Dreyssena  polymorpha.  Individuals  old  and 
young  were  often  seen  grouped  together  in  colonies  which 
sometimes  extended  completely  over  the  sponges.  But  what 


1 66  THE   MICROSCOPY   OF  DRINKING-WATER. 

most  of  all  attracted  attention  was  a  luxuriant  growth  of 
the  4  horn-polyp,'  Cordylophora  lacustris.  It  covered  the 
mussel-shells  and  occupied  all  the  space  between  the  sponges. 
The  stalks  reached  a  length  of  an  inch  or  more.  On  and 
between  the  Cordylophora  swarmed  countless  numbers  of 
Vorticella,  Acineta,  and  other  Protozoa  and  Rotifera.  These 
organisms  had  no  lack  of  food-material,  and  the  absence  of 
light  protected  them  from  many  foes  which,  in  the  light,  thin 
out  their  ranks.  Over  all  these  animals  Crenothrix  was  found 
growing  in  abundance.  The  shells  of  the  mussels  and  the 
stems  of  the  'horn-polyps  '  were  coated  with  a  thick  felt-like 
layer  of  these  'iron-bacteria/  In  other  localities  in  the 
pipes  the  place  of  the  'horn-polyps'  was  occupied  by  the 
Bryozoa,  or  'Moss-animalcules.'  All  of  these  branching 
forms  were  spoken  of  collectively  by  the  workmen  as  *  pipe- 
moss.'  " 

In  the  summer  of  1896,  when  the  pipes  of  the  Metropoli- 
tan Water  Works  were  being  laid  in  Beacon  Street,  Boston, 
near  the  Chestnut  Hill  reservoir,  a  i6-inch  main  leading  from 
the  Fisher  Hill  reservoir  to  the  Brighton  district  was  opened. 
This  afforded  an  opportunity  to  examine  the  material  on  the 
inside  of  a  pipe  that  had  been  laid  ten  years.  Inspection 
showed  that  besides  the  usual  coating  of  iron-rust,  tubercles, 
etc.,  there  were  numerous  patches  of  fresh-water  sponge  (both 
Spongilla  and  Meyenia),  brownish  or  almost  white  in  color, 
and  about  the  size  of  the  palm  of  one's  hand.  What  was 
most  conspicuous,  however,  was  a  sort  of  brown  matting 
which  covered  much  larger  areas,  and  which  had  a  thickness 
•of  about  i  inch.  It  had  a  very  rough  surface  and,  when 
dried,  reminded  one  of  a  piece  of  coarse  burlap.  This  proved 
to  be  an  animal  form  belonging  to  the  Bryozoa,  known  as 
JFredericella.  As  fragments  of  it  had  several  times  before 


GROWTH   OF   ORGANISMS  IN    WATER-PIPES.  1 67 

been  observed  in  the  water  from  the  service-taps,  and  as  it 
had  been  seen  growing  in  some  small  pipes  connected  with 
the  filtration  experiments  at  the  Chestnut  Hill  reservoir,  more 
extended  observations  were  made  in  different  parts  of  the 
distribution  system. 

These  brought  out  the  fact  that  sponges  and  the  Bryozoa 
were  well  established  in  the  pipes.  Many  other  organisms 
were  also  observed.  In  some  places  almost  pure  cultures  of 
Stentor  and  Zoothamnium  were  found.  At  other  points 
hosts  of  different  organisms  were  seen,  such  as  snails,  mussels, 
Hydra,  Nais,  and  Anguillula,  Acineta,  Vorticella,  Arcella, 
Amoeba,  countless  numbers  of  ciliated  infusoria,  and  many 
other  forms.  The  growths  were  distinctly  animal  in  their 
nature,  but  in  many  places  parasitic  vegetable  forms,  such  as 
Achlya,  Crenothrix,  Leptothrix,  etc.,  were  common.  The 
most  important  class  of  organisms  found,  however,  was  the 
Bryozoa,  of  which  Fredericella  and  Plumatella  were  the 
chief  representatives. 

The  fact  that  the  organisms  that  dwell  in  water-pipes 
depend  for  their  food-material  upon  the  algae,  protozoa, 
etc.,  contained  in  the  water  may  be  easily  demonstrated  by 
experiment.  Specimens  of  Fredericella  and  Plumatella  were 
once  placed  in  a  series  of  jars,  some  of  which  were  supplied 
with  water  rich  in  its  microscopic  contents,  while  others  were 
supplied  with  the  same  water  after  filtration.  All  the  jars 
were  kept  in  semi-darkness  at  the  same  temperature,  and  were 
examined  daily.  The  Fredericella  and  Plumatella  that  had 
been  supplied  with  filtered  water  soon  began  to  die,  while 
those  in  the  other  jars  lived  as  long  as  the  experiment  was 
continued.  Some  of  the  same  Bryozoa  were  placed  in  jars 
furnished  with  water  from  the  Newton  supply,*  and  after 

*  A  ground-water  almost  free  from  microscopic  organisms. 


1 68  THE   MICROSCOPY   OF  DRINKING-WATER. 

about  a  week  they  died  for  want  of  food.  Dr.  G.  H.  Parker* 
once  made  a  similar  experiment  on  fresh-water  sponge,  and 
obtained  the  same  result.  With  these  facts  established,  we 
may  confidently  affirm  that  fresh-water  sponge,  Bryozoa,  and 
similar  pipe-dwellers  will  be  absent  from  water-pipes  where 
ground-water  or  water  that  has  been  effectively  filtered  is 
used. 

One  naturally  asks,  "  What  is  the  effect  of  these  organ- 
isms growing  in  the  pipes?  "  In  a  certain  sense  they  tend  to 
improve  the  quality  of  the  water  by  reducing  the  number  of 
floating  microscopic  organisms;  but  they  themselves  must 
in  time  decay,  and  any  one  whose  nose  has  ever  had  an  experi- 
ence with  decomposing  sponge  will  appreciate  the  fact  that 
better  places  for  these  organisms  may  be  found  than  the  dis- 
tribution systems  of  our  water-supplies.  It  should  be  stated, 
however,  that  in  all  probability  very  large  quantities  would 
be  required  to  produce  tastes  or  odors  that  would  be 
noticed  in  the  water.  Perhaps  the  greatest  objection  to  their 
presence  is  the  fact  that  they  tend  to  impede  the  flow  of 
water  in  the  pipes.  When  one  considers  that  a  coating  J  inch 
thick  diminishes  the  area  of  the  cross-section  of  a  24-inch  pipe 
by  4#,  and  of  a  6-inch  pipe  by  15$,  and  when  one  learns  that 
these  organisms  often  form  layers  even  thicker  than  this,  it 
will  be  seen  that  such  growths  are  matters  of  no  little  impor- 
tance. Furthermore,  fingers  of  the  fresh-water  sponge  some- 
times extend  several  inches  into  the  water,  and  the  matting 
of  the  Bryozoa  is  always  rough  on  account  of  the  stiff 
branches  that  are  extended  in  order  that  the  organisms 
may  secure  their  food.  This  roughness  of  the  surface  must 


*  G.  H.  Parker,  Experiments  on  Fresh-water  Sponge,  Special  Report  of 
the  Massachusetts  State  Board  of  Health,  1890,  p.  618. 


GROWTH  OF  ORGANISMS  IN    WATER-PIPES.  169 

increase  the  friction  of  the  pipe  by  a  considerable  but  indefinite 
amount. 

Organisms  growing  on  the  inner  walls  of  water-pipes  tend  to 
promote  tuberculation.  This  takes  place  in  the  following  manner : 
Between  the  organisms  and  the  walls  of  the  pipe  there  is  a  layer 
of  water  from  which  the  oxygen  is  at  times  temporarily  exhausted 
and  in  which  carbonic  acid  is  abundant,  these  conditions  being 
brought  about  by  the  organisms.  If  the  organisms  are  torn  away 
the  pipe- coating  may  be  removed  and  a  little  spot  of  iron  thus 
exposed  to  the  action  of  'the  'carbonic  acid.  Corrosion  thus 
begins  and  iron  oxide  becomes  deposited  in  crystalline  form 
around  this  spot,  forming  what  is  known  as  a  tubercle.  These 
tubercles  greatly  increase  the  roughness  of  the  pipe  and  conse- 
quently retard  the  flow  of  water. 

An  interesting  experience  with  pipe  moss  is  on  record  at 
the  Brooklyn  Water  Department.  In  November,  1897,  the 
water  in  the  Mt.  Prospect  reservoir  became  so  filled  with  Asterio- 
nella  that  it  was  deemed  advisable  to  shut  off  the  reservoir  and 
pump  directly  into  the  pipes.  This  action  was  followed  by  the 
appearance  of  brown  fibrous  masses  in  the  tap-water.  In  a 
number  of  instances  this  fibrous  matting  stopped  up  the  taps, 
and  even  large  pipes  were  choked.  The  water  at  the  same  time 
had  a  distinctly  moldy  and  unpleasant  odor.  The  fibrous  mat- 
ting proved  to  be  Paludicella.  It  had  been  growing  on  the  inner 
walls  of  the  pipes,  and  the  change  of  currents  and  the  pulsations 
of  the  pump,  due  to  the  direct  pumping  into  the  pipes,  had  dis- 
lodged it.  Systematic  and  thorough  flushing  of  the  pipes  materi- 
ally improved  the  conditions. 


PART   II. 


CHAPTER    XIV. 

CLASSIFICATION    OF   THE  MICROSCOPIC   ORGANISMS. 

THE  microscopic  organisms  found  in  drinking-water  in- 
clude the  lowest  forms  of  life.  Some  of  them  belong  to  the 
vegetable  kingdom,  some  belong  to  the  animal  kingdom, 
while  others  possess  characteristics  that  pertain  to  both. 
There  is  in  reality  no  sharp  dividing-line  between  the  vege- 
tal and  the  animal  in  the  low  forms  of  life.  Nature's 
boundaries  are  always  shaded  on  both  sides. 

Classification  of  organisms  into  groups  is  necessary,  but  it 
must  be  borne  in  mind  that  all  classifications  are  artificial 
.and  subject  to  change.  The  one  outlined  below  and  used 
throughout  this  volume  is  believed  to  be  the  most  convenient 
for  the  work  at  hand.  A  number  of  groups,  not  pertaining  to 
the  microscopical  examination  of  drinking-water,  are  omitted. 

CLASSIFICATION  OF  THE  MICROSCOPIC  ORGANISMS. 
Plants. 

DIATOMACE^E.  ALG^E  (in  the  narrower  sense). 

SCHIZOPHYCE.E.  Chlorophycea. 

Schizomycetes.  FUNGI. 

Cyanophycea.  VARIOUS  HIGHER  PLANTS. 

171 


1/2  THE  MICROSCOPY  OF  DRINKING-WATER. 

Animals. 

PROTOZOA.  CRUSTACEA. 

Rhizopoda.  Entomostraca. 

Mastigophora  (Flagellata).  BRYOZOA  (POLYZOA). 

Infusoria  (in  the  narrower  sense).  SPONGID^E. 

ROTIFERA.  VARIOUS  HIGHER  ANIMALS* 


CHAPTER    XV. 
DIATOMACE^E. 

THE  Diatomaceae  comprise  a  group  of  minute  vegetable 
forms  of  a  low  order.  Their  exact  position  in  the  scale  of  life 
has  been  the  subject  of  much  controversy.  The  early  writers 
considered  them  to  belong  to  the  animal  kingdom  because 
of  the  power  of  movement  that  some  of  them  possess.  Later, 
when  they  had  become  generally  recognized  as  plants,  they 
were  considered  as  a  Class  or  Order  of  the  Algae.  Recent 
cryptogamists,  however,  prefer  to  class  them  as  an  inde- 
pendent group,  thereby  recognizing  the  fact  that  they  are 
quite  different  from  most  unicellular  plants.  This  differ- 
ence lies  chiefly  in  the  possession  of  siliceous  cell-walls  upon 
which  may  be  observed  certain  markings  that  are  constant  in 
size  and  arrangement  for  each  species.  The  great  beauty  of 
these  markings,  together  with  the  infinite  variety  in  the  sizes 
and  shapes  of  the  ceils  of  different  species,  have  long  made 
them  objects  of  special  study  by  microscopists. 

Diatom  Cells. — A  diatom  cell  is  constructed  like  a  box. 
There  is  a  top  and  a  bottom,  known  as  the  upper  and  lower 
valve,  on  both  of  which  markings  are  found.  The  valves  are 
connected  by  membranes  known  as  "sutural  zones,"  "  con- 
nective membranes,"  "  girdles,"  or,  when  detached,  as 
*'  hoops."  There  are  two  of  these  membranes,  one  attached 
to  each  valve,  and  they  are  so  arranged  that  one  slides  over 

173 


174  THE   MICROSCOPY   OF  DRINKING-WATER. 

the  other  just  as  the  rim  of  a  box-cover  fits  over  the  sides. 
This  arrangement  may  be  seen  in  Plate  I,  Figs.  A,  B,  and 
C,  where  a  typical  diatom,  Navicula  viridis,  is  shown  in  three 
views.  A  represents  the  valve  *  view  of  the  diatom,  that  is, 
the  view  seen  when  looking  directly  at  the  valve  or  the  top  of 
the  box.  B  represents  the  girdle*  view,  the  view  seen  when 
looking  at  the  connective  membrane.  C  is  a  cross-section 
through  the  diatom. 

The  upper  or  outer  valve  is  indicated  by  a,  and  its  connec- 
tive membrane  by  c.  The  girdle  view  shows  how  this  connec- 
tive membrane  of  the  larger  valve  fits  over  a  similar  one,  c\ 
attached  to  the  lower  or  smaller  valve,  b.  These  girdles  have 
the  power  of  sliding  one  upon  the  other  so  that  the  thickness 
of  the  diatom,  i.e.  the  distance  between  the  valves,  is 
variable. 

The  valves  of  the  diatom  shown  in  the  figure  are  covered 
with  furrows  or  markings,  g.  At  the  centre  and  at  each  end 
there  are  slight  thickenings  of  the  cell-wall,  known  as  nodules. 
The  central  one  is  called  the  central  nodule,  d,  and  those  at 

*  The  terms  used  by  different  writers  to  express  these  two  views  of  a 
diatom  are' very  confusing.  In  the  following  list  the  terms  under  A  repre- 
sent the  valve  view  and  those  under  B  the  girdle  view. 

A  B 

Valve  view.  Girdle  view. 

Side  view.  Front  view. 

Top  view.  Zonal  view. 

Face  valvaire.  Face  connective. 

Primary  side.  Secondary  side. 

Secondary  side.  Primary  side. 

Vue  de  profil.  Vue  de  face. 

The  terms  "side  view"  and  "front  view"  are  those  generally  used  by 
English  and  American  diatomists,  but  the  author  has  avoided  them  as  not 
being  in  themselves  sufficiently  clear,  and  has  preferred  to  use  the  less 
euphonious  but  more  self-explanatory  terms,  "valve  view"  and  "girdle 
view."  In  consulting  books  on  diatoms  the  reader  should  be  careful  to 
note  the  way  in  which  the  two  views  are-designated. 


D I  A  TO  MA  CEJE.  1 7  5 

the  ends,  terminal  nodules,  e,  e.  Between  these  nodules  and 
extending  along  the  medial  line  of  the  valve  there  is  a  sort  of 
ridge,  /,  in  which  there  is  a  furrow  called  a  raphe,  or  raphe. 
Through  this  the  living  matter  of  the  diatom  probably  com- 
municates with  the  outer  world.  The  slit  is  supposed  to  be 
somewhat  enlarged  at  the  nodules.  The  raphe,  the  nodules, 
and  the  markings,  taken  in  connection  with  the  shape  and  size 
of  the  valves,  are  the  most  important  external  features  of  a 
diatom  and  are  the  first  to  be  considered  in  studying  them. 

Shape  and  Size. — There  is  probably  no  class  of  unicellu- 
lar organisms  in  which  the  outlines  vary  more  than  in  those  of 
the  diatoms.  From  the  straight  line  to  the  circle  almost  all 
the  geometrical  figures  may  be  found.  Some  of  these  may  be 
described  as  circular,  oval,  oblong,  elliptical,  saddle-shaped, 
boat-shaped,  triangular,  undulate,  sigmoid,  linear,  etc.  The. 
variations  in  shape  are  most  marked  in  the  valve  view.  The 
girdle  view,  as  a  rule,  is  more  or  less  rectangular.  The  valves 
are  usually  plane  surfaces,  with  only  slight  curvatures  or 
undulations.  Occasionally  the  surface  is  warped  as  in  Am- 
phiprora  and  Surirella.  As  a  rule  the  two  valves  of  a  frustule 
are  nearly  parallel,  but  in  such  forms  as  Meridion,  Gom- 
phonema,  etc.,  the  frustule  is  wedge-shaped  when  seen  in 
girdle  view.  The  most  varied  forms  are  found  in  salt  or 
brackish  water,  and  the  common  fresh-water  forms  are  so 
simple  and  so  characteristic  that  the  reader  will  have  little 
difficulty  in  assigning  them  their  proper  generic  names. 
Some  genera  have  the  cell  divided  more  or  less  completely  by 
internal  plates,  called  septa,  when  fully  developed  as  in 
Rhabdonema;  and  vittae,  when  incomplete  as  in  Gramma- 
tophora.  Some  diatoms  have  external  expansions  on  the  mar- 
gin of  the  valves.  Surirella,  for  example,  has  thin  expansions 
known  as  alae,  or  wings.  When  these  alae  are  imperfectly 


THE   MICROSCOPY   OF  DRINKING-WATER. 

developed  they  are  called  keels.  Nitzschia  for  this  reason 
is  said  to  be  carinate.  These  wings  or  keels  usually  extend 
along  the  border  of  the  raphe.  Certain  filamentous  forms, 
such  as  Melosira,  have  processes  at  the  point  of  attachment. 
In  others  these  processes  are  elongated  into  horns,  or  bristles. 

Diatoms  vary  in  size  from  the  minute  Cyclotella,  less  than 
10  microns*  in  diameter,  to  such  large  forms  as  Surirella  and 
Navicula,  that  sometimes  are  one  millimeter  long.  Some 
filamentous  forms  grow  to  a  considerable  length, — often 
several  feet. 

Markings. — The  valves  of  most  diatoms  are  marked  with 
lines  or  points.  In  many  cases  the  lines  may  be  resolved 
into  series  of  points,  pearls,  beads,  or  striae,  when  a  higher 
power  of  the  microscope  is  used.  The  variations  in  the 
number  and  size  of  these  points  and  their  uniformity  in  differ- 
ent individuals  of  the  same  species  make  them  convenient 
objects  for  testing  the  resolving  power  of  microscopes.  The 
variation  in  the  number  of  these  striae  may  be  seen  from  the 
following  table : 

Number  of  Striae  per  Millimeter. 

Longitudinal.  Transverse. 

Epithemia  ocellata,  Kz 800  430 

Navicula  major,  Kz 850  630 

"         viridis,  Kz 2400  720 

lyra 850  1000 

Cymbella  navicula,  Ehb 1200  1500 

Pleurosigma  angulatum,  Sm 1580  2100 

Synedra  pulchella,  Kz 670  2150 

Navicula  rhomboides 1700  2700 

Amphipleura  pellucida,  Ktz 3400  3700  to  5200 

The   extreme   minuteness   of  these  points,   their  various 
appearances  under  different  conditions,  and  the  difficulty  of 
studying  them  even  with  microscopes  of  the  highest  magnify- 
ing powers,  have  given  rise  to  many  different  theories  concern- 
*  One  micro-millimeter,  or  micron  (//),  equals  .001  millimeter. 


DIATOMACEsE. 


177 


ing  the  character  of  the  valves.  Some  writers  insist  that  the 
points  are  elevations:  others  claim  that  they  are  depressions. 
Recent  students  agree  that  the  structure  is  more  complex  than 
was  formerly  considered  to  be  the  case.  The  following  con- 
ception of  M.  J.  Deby,  while  perhaps  not  correct  for  all  cases, 
is  a  good  illustration  of  the  modern  view  (see  Fig.  22). 

d  \  d' 


C 

c' 

n 

n' 

TRICERATIUM 

PLEUROSIGMA 

FIG.  22. — TRANSVERSE  SECTION  OF  A  DIATOM  VALVE.     (After  Deby.) 
4i.   Upper  (outer)  layer.  d.   Inter-alveolar  pillars. 

b.   Lower  (inner)  layer.  m.  Thin  part  of  upper  layer. 

t.   Cavities.  «.  Bottom  of  alveolae. 

"The  valves  of  most  diatoms  are  composed  of  two  layers, 
between  which  there  are  circular  or  hexagonal  cavities 
bounded  by  walls  of  silica.  The  upper  layer  is  not  uniform 
in  thickness,  but  is  thin  just  above  the  cavities,  and  thicker, 
rising  in  pointed  or  rounded  prominences,  above  the  intersec- 
tion of  the  walls  of  the  cavities.  The  upper  layer  is  lightly 
silicified,  and  the  thin  portions  are  easily  broken,  making 
openings  into  the  cavities.  The  lower  layer  bears  varied 
designs  the  nature  of  which  has  not  been  well  established. 
What  authors  have  described  as  areolae,  pearls,  pores,  orifices, 
granular  projections,  depressions,  hexagons,  beads,  points, 
etc.,  are  really  one  and  the  same  thing." 

Cell-contents. — The  frustule  of  a  diatom  is  somewhat 
analogous  to  the  shell  of  a  bivalve, — the  living  matter  is 
inside.  Just  inside  the  cell-wall  there  is  a  thin  protoplasmic 
lining  (primordial  utricle).  This  protoplasm  sends  radiating 
streams  through  the  cell,  and  it  is  possible  that  a  portion  of 


1/8  THE  MICROSCOPY   OF  DRINKING-WATER. 

it  extends  through  the  openings  in  the  cell-wall  and  communi- 
cates with  the  outer  world.  It  is  this  layer  of  protoplasm  also* 
that  secretes  the  silica  of  the  cell-wall.  Between  the  streams 
of  protoplasm  (PI.  I,  Fig.  C)  there  are  what  appear  to  be 
empty  cavities.  In  or  on  the  borders  of  these,  oil-globules 
may  be  sometimes  observed.  There  is  a  nucleus,  and 
probably  a  nucleolus,  located  near  the  centre  of  the  cell. 
The  most  conspicuous  portion  of  the  cell-contents,  however,, 
consists  of  colored  lumps  or  plates,  which  are  usually  constant 
in  appearance  and  position  for  any  particular  species.  The 
brown  coloring  matter  of  these  "chromatophore  plates"  is 
known  as  diatomin.  It  is  a  substance  analogous  to  chloro- 
phyll and  has  been  considered  by  some  writers  to  be  a  com- 
pound of  chlorophyll  and  phycoxanthin.  The  spectrum  of 
diatomin  is  very  similar  to  that  of  chlorophyll.  There  are 
two  absorption-bands, — one  between  B  and  C  in  the  orange- 
yellow,  and  one  between  E  and  F  in  the  indigo-violet. 
Diatomin  is  soluble  in  dilute  alcohol,  giving  a  brownish-yellow 
solution  that  is  sometimes  very  slightly  fluorescent.  When 
dried  or  treated  with  concentrated  sulphuric  acid  it  assumes  a 
green  color.  When  living  diatoms  are  exposed  to  the  direct 
rays  of  the  sun  or  subjected  to  heat  for  a  considerable  time 
the  color  of  the  chromatophore  plates  changes  from  brown 
to  green.  In  certain  species  other  internal  features  have 
been  noted ;  namely,  the  contractile  zonal  membrane,  the 
germinative  dot,  double  nucleus,  etc.,  but  of  these  there  is 
little  known. 

External  Secretions. — Living  diatoms  are  covered  with 
a  transparent  gelatinous  envelope,  which  is  probably  a  secre- 
tion from  the  protoplasm.  In  many  species  it  is  very  thin 
and  can  be  discerned  only  by  the  use  of  staining  agents.  In 
the  filamentous  and  chain-forming  species  it  serves  to  hold 


DIATOMACE&. 

the  frustules  together.  In  Tabellaria,  for  example,  little 
lumps  of  the  gelatinous  substance  may  be  seen  at  the  corners 
of  the  frustules  at  the  point  of  attachment.  Some  species 
secrete  great  quantities  of  gelatinous  material  and  are  entirely 
embedded  in  it.  In  a  few  cases  it  is  of  a  firmer  consistency' 
and  forms  tubes,  stalks,  or  stipes,  upon  the  ends  of  which 
the  frustules  are  seated.  These  stalks  attach  themselves  to 
stones,  wood,  etc.,  immersed  in  the  water. 

Movement. — Some  of  the  diatoms  exhibit  the  phenome- 
non of  spontaneous  movement.  This  has  always  excited 
interest  and  has  been  the  subject  of  much  speculation.  It 
was  the  chief  argument  advanced  by  the  early  writers  for 
placing  the  diatoms  in  the  animal  kingdom.  The  most 
peculiar  movement  is  that  of  Bacillaria  paradoxa,  whose  frus- 
tules slide  over  each  other  in  a  longitudinal  direction  until 
they  are  all  but  detached,  and  then  stop,  reverse  their  motion, 
and  slide  backwards  in  the  opposite  direction  until  they  are 
again  all  but  detached.  This  alternate  motion  is  repeated  at 
quite  regular  intervals.  Some  of  the  free  species  show  the 
greatest  movement,  and  of  these  Navicula  is  one  of  the  most 
interesting.  Its  motion  has  been  described  as  "  a  sudden 
advance  in  a  straight  line,  a  little  hesitation,  then  other 
rectilinear  nrovements,  and,  after  a  short  pause,  a  return  upon 
nearly  the  same  path  by  similar  movements."  The  move- 
ment appears  to  be  a  mechanical  one.  The  diatoms  do  not 
turn  aside  to  avoid  obstacles,  although  their  direction  is 
sometimes  changed  by  them.  The  rapidity  of  their  motion 
has  been  calculated  to  be  "400  times  their  own  length  in 
three  minutes."  Their  motion  shows  the  expenditure  of  con- 
siderable force.  Objects  50  or  100  times  their  size  are  some- 
times pushed  aside. 

Various  hypotheses  have  been  advanced  to  account  for  the 


l8o  THE  MICROSCOPY  OF  DRINKING-WATER. 

movement  of  diatoms.  Naegeli  suggested  that  it  was  due  to 
endosmotic  and  exosmotic  currents;  Ehrenberg  claimed  that 
the  movement  was  due  to  cilia;  another  writer,  that  it  was 
caused  by  a  snail-like  foot  outside  the  frustule;  another,  that 
it  was  due  to  a  layer  of  protoplasm  covering  the  raph£. 
H.  L.  Smith,  after  much  study,  came  to  the  conclusion  "  that 
the  motion  of  Naviculae  is  due  to  injection  and  expulsion  of 
water,  and  that  these  currents  are  caused  by  different  tensions 
of  the  internal  membranous  sac  in  the  two  halves  of  the 
trustule." 

In  spite  of  all  the  study  that  has  been  given  to  the  sub- 
ject, we  must  admit  that  the  cause  of  the  movement  of 
diatoms  is  unknown.  The  "cilia  theory"  seems  the  most 
probable,  but  it  is  doubtful  if  the  cilia  are  more  than  mucous 
threads. 

Multiplication. — Diatoms  multiply  by  a  process  of  halv- 
ing or  splitting,  the  Greek  word  for  which  gives  rise  to  the 
name  diatom.  The  cell-division  is  similar  to  that  in  all  plants, 
but  in  this  case  the  process  is  of  especial  interest  because  of 
the  rigid  character  of  the  cell-walls. 

The  process  begins  by  a  division  of  the  nucleus  and 
iiucleolus.  The  protoplasm  expands  or  increases  in  bulk, 
forcing  the  valves  apart,  the  hoops  sliding  one  out  of  the 
other.  The  two  halves  of  the  nucleus  separate,  the  diatomin 
collects  at  either  side,  and  a  membrane  forms,  dividing  the  cell 
into  two  parts.  Finally  the  two  parts  separate.  The  newly 
formed  membrane  becomes  charged  with  silica,  making  a  new 
valve,  and  soon  after  its  hoop  develops.  This  process  is  well 
illustrated  by  a  drawing  of  M.  J.  Deby,  shown  on  PL  I, 
Figs.  D,E,  and  F.  Sometimes  the  frustules  separate  entirely ; 
sometimes  they  remain  attached  forming  filaments,  as  in  Mel- 
osira,  bands  as  in  Fragiiaria,  or  zigzag  chains  as  in  Tabellaria. 


DIA  TO  MA  CEJZ.  1  8  1 

The  above  is  the  usually  accepted  theory  of  cell-division. 
It  is  probably  correct  in  many,  if  not  in  most  cases.  It 
assumes  that  the  siliceous  walls  are  not  able  to  expand,  and 
the  result  is  that  after  repeated  division  the  frustules  become 
smaller.  It  is  claimed  that  in  some  cases  the  cell-wall  does 
expand,  and  therefore  that  the  size  of  the  frustules  does  not 
decrease  after  division. 

The  generally  accepted  theory  of  cell-division  assumes  that 
a  diatom  frustule  has  two  valves,  one  the  larger  and  older, 
and  the  other  the  smaller  and  younger.  After  division  two 
cells  are  formed,  one  equal  in  size  to  the  larger  valve  and  the 
other  equal  to  the  smaller  one,  the  difference  in  size  being 
twice  the  thickness  of  the  hoop.  This  theory  also  assumes 
that  both  the  mother-  and  the  daughter-cell  have  the  power 
of  further  division.  From  these  assumptions  certain  laws  of 
multiplication  may  be  deduced.  For  example:  If  A  is  the 
parent  cell, 

After  one  period    of  time,  /,  A  will  have  produced  B\ 
4<      two  periods"      "    2t,  A    "      "  "         £'  ', 

and    B    "       "  "          C\ 

"      three     "        "      "    $/,  A    "      "  "         B", 

B    li      il  "         C", 

B'  "      "  "          C\ 

C   "      "  "        D\ 

and  so  on. 

From  this  it  happens  that 

After  t  we  have  \A  +  iB\ 
"   2t  "      "      lA  +  2B  +  C; 


and  so  on. 
The  laws  may  be  expressed  mathematically  as  follows: 


1 82  THE   MICROSCOPY   OF  DRINKING-WATER. 

1.  As    the    number   of    periods  of    division    increases    in 
arithmetical  progression  the  total  number  of  frustules  increases 
in  geometrical  progression. 

2.  The  number  of  frustules  equal  in  size  after  any  period 
of    division   are    represented    by  the  terms  of   the    binomial 
theorem  (a  -f-  <£)",  where  a  and  b  are  unity. 

These  laws  have  been  demonstrated  experimentally,  the 
first  by  the  author*  and  the  second  by  Miquel.f 

Reproduction. — The  continued  process  of  multiplication 
results  in  a  constant  diminution  in  the  size  of  the  frustules. 
After  a  certain  minimum  limit  of  size  has  been  reached  or 
after  their  power  of  multiplication  has  become  exhausted,  a 
reproductive  process  takes  place.  Usually  this  consists  of  a 
conjugation  which  results  in  the  formation  of  a  large  cell,  or 
auxospore,  capable  of  reproducing  a  frustule  of  large  size 
which,  by  multiplication,  gives. rise  to  a  new  series  of  frustules 
like  the  first.  This  theory,  known  as  "  Pfitzer's  Auxospore 
Theory,"  was  advanced  in  1871.  Count  Castracane  has 
shown  that  its  application  is  not  universal,  and  that  in  the  case 
of  some  diatoms  reproduction  takes  place  through  the  forma- 
tion of  spores,  or  "  gonids, "  which  become  fertilized  by 
conjugation  and,  after  a  period  of  repose,  attain  a  condition 
for  living  an  independent  life  and  reproducing  in  every 
respect  the  adult  type  of  mother-cell.  The  author  has  ob- 
served these  spore-like  bodies  in  the  cells  of  Asterionella. 

There  are  few  reliable  data  to  be  found  in  regard  to  the 
reproduction  of  diatoms.  True  conjugation  has  been  observed 
in  comparatively  few  genera.  It  is  believed  that  there  are 
four  methods  of  conjugation.  First,  a  single  frustule,  self- 
fertilized,  producing  one  sporange  and  one  auxospore;  second, 

*  G.  C.   Whipple,   "Some  Observations  on  the  Growth  of  Diatoms  in 
Surface  Waters."     Tech.  Quar.,  vol.  vn.,  No.  3.  Oct.  1894. 
fP.  Miquel,.Annales  de  Micrographie,  No.  n,  1892. 


D I  A  TO  MA  CE&.  1 8  3 

a  single  frustule,  self-fertilized,  producing  two  sporanges  and 
two  auxospores;  third,  two  conjugating  frustules,  with  un- 
differentiated  endochrome,  producing  one  sporange  and  one 
auxospore;  fourth,  two  conjugating  frustules,  with  differen- 
tiated endochrome,  producing  two  sporangial  cells,  one  of 
which  is  sometimes  abortive.  Good  examples  of  conjugation 
may  be  found  in  Surirella  splendida,  Epithemia  turgida,  and 
in  various  species  of  Melosira.  The  sporangial  frustules  of 
JVlelosira  (shown  in  PL  III,  Fig.  I/)  are  quite  common. 

Classification  of  Diatoms. — Several  methods  of  classifi- 
cation of  diatoms  have  been  proposed,  but  only  two  are 
worthy  of  attention,  and  even  these  must  be  considered  as 
provisional. 

The  most  recent  is  that  proposed  by  Pfitzer  and  elaborated 
by  Petit.  It  is  based  upon  two  assumptions, — namely,  that 
the  internal  disposition  of  the  endochrome  is  constant  for  all 
individuals  of  the  same  species,  and  that  the  relation  between 
the  frustule  and  the  endochrome  is  fixed  and  common  to  all 
species  of  the  same  genus.  The  family  Diatomaceae  is  divided 
into  two  sub-families,  the  Placochromaticeae  and  the  Cocco- 
chromaticeae.  The  genera  of  the  first  sub-family  have  the 
endochrome  arranged  in  plates  or  layers,  and  those  of  the 
second  sub-family,  in  lumps  or  small  granular  masses. 
Secondary  classification  into  tribes,  etc.,  depends  upon  the 
symmetry  of  the  valves  with  reference  to  the  axes,  the  dis- 
similarity of  the  valves  of  a  single  frustule,  the  presence  or 
absence  of  an  intervalvular  diaphragm,  the  raphe,  nodules, 
etc.  There  is  little  to  be  said  in  favor  of  this  system,  but  it 
is  worthy  of  study  as  the  authors  have  tried  to  do  what  has 
been  long  neglected, — namely,  to  emphasize  the  study  of  the 
entire  cell  with  its  contents  rather  than  to  confine  the  atten- 
tion wholly  to  the  cell-wall  or  frustule. 


1 84  THE   MICROSCOPY   OF  DRINKING-WATER. 

The  most  useful  system  of  classification  and  the  one 
generally  recognized  is  that  suggested  by  H.  L.  Smith.  It 
is  based  almost  entirely  on  the  morphology  of  the  frustule. 
This  has  the  advantage  of  enabling  one  to  classify  both  living 
and  fossil  forms,  but  it  has  tended  to  divert  observers  from 
the  study  of  the  diatom  as  a  living  cell  to  the  study  of  the 
shell  alone. 

According  to  Smith's  classification  the  Diatomaceae  are 
divided  into  three  tribes  characterized  by  the  presence  or 
absence  of  a  raphe.  An  outline  of  this  classification,  together 
with  descriptions  of  the  genera  most  common  in  drinking- 
water,  is  given  below.  The  names  of  the  genera  are  printed 
in  heavy  type. 

TRIBE   I.     RAPHIDIE^E. 

Always  possessing  a  distinct  raphe  on  one  or  both  valves. 
Central  nodule  generally  present  and  conspicuous.  Frustules 
mostly  bacillar  in  valve  view;  sometimes  broadly  oval;  with- 
out spines  or  other  processes.  Navicula  major  is  the  typical 
form. 

FAMILY  CYMBELLE^E. — Raphe  mostly  curved.  Valves  alike,  more 
or  less  arcuate,  cymbiform. 

Amphora. 

Frustules  single,  ovoidal  in  girdle  view,  the  girdle  often  striated 
or  longitudinally  punctate.  Valves  extremely  unsymmetrical, 
with  a  convex  and  concave  side,  with  an  eccentric  raphe,  with 
medial  and  terminal  nodules.  The  raphe  is  sometimes  near 
the  convex  side,  sometimes  near  the  concave  side,  and  the 
medial  nodule  is  often  away  from  the  centre.  There  are  trans- 
verse striae,  radiating  somewhat  from  the  medial  nodule.  This 
genus  is  very  ornate.  There  are  a  number  of  species,  none 
of  them  very  common  in  water.  (PI.  I,  Figs,  i  and  2 . ) 
Cymbella. 

Frustules  generally  single,  elongated,  symmetrical  with  respect 


D I  A  TO  MA  CE&.  1 8  $ 

to  the  minor  axis.  Valves  more  or  less  arched,  with  one  side 
very  convex  and  the  other  side  slightly  or  not  at  all  convex ; 
asymmetrically  divided  by  a  curved  raphe  ;  possessing  terminal 
and  medial  nodules  ;  marked  by  transverse  bead-like  striae, 
which  do  not  extend  to  the  raphe,  but  have  a  clear  space,  wider 
at  the  medial  nodule  than  elsewhere.  There  are  a  number  of 
common  species.  (PI.  I,  Figs.  3  and  4.) 

Encyonema. 

Frustules,  when  young,  enclosed  in  a  hyaline  mucilaginous 
tube,  in  which  they  multiply  by  division,  pushing  each  other 
forward  in  an  alternately  inverse  position.  Valves  symmetrical 
with  respect  to  the  minor  axis,  convex  on  one  side,  straight 
on  the  other,  with  rounded  extremities  that  project  beyond 
the  straight  side.  A  straight  raphe  divides  the  valves  into  two 
unequal  parts.  There  are  medial  and  terminal  nodules.  The 
striae  are  transverse  or  radiating  somewhat  from  the  medial 
nodule.  There  is  a  clear  space  around  the  medial  nodule,  but 
elsewhere  the  striae  approach  closely  to  the  raphe.  There  are 
several  species.  (PI.  I,  Fig.  5.) 

Cocconema. 

Frustules,  when  young,  borne  singly  or  in  pairs  on  filamentous 
pedicels,  which  may  be  simple  or  branched.  They  form  muci- 
laginous layers  on  submerged  objects.  Later  they  become  free- 
swimming.  The  valves  are  long,  large,  strongly  arched, 
convex  on  one  side,  concave  on  the  other  side  save  for  a  little 
inflation  in  the  middle.  The  raphe  is  curved.  There  are 
medial  and  terminal  nodules.  The  striae  are  rather  large  pearls, 
transverse,  with  very  slight  radiation,  and  not  approaching  the 
raphe  closely.  (PI.  I,  Fig.  6.) 

FAMILY   NAVICULE^E. — Valves  symmetrically  divided  by  the  raph£. 
Frustules  not  cuneate  or  cymbiform. 

Navicula. 

Frustules  single,  symmetrical  with  respect  to  both  axes.  Valves 
naviculoid,  or  boat-shaped;  of  various  proportions,  some  very 
long  and  narrow,  others  short  and  wide,  others  ellipsoidal ; 
with  straight  or  slightly  curving  sides  ;  with  ends  pointed  or 
rounded.  There  is  a  straight  raphe  with  conspicuous  medial 


186  THE   MICROSCOPY   OF  DRINKING-WATER. 

and  terminal  nodules.  The  valves  are  marked  with  transverse 
furrows,  that  have  a  slight  radial  tendency.  The  frustules  are 
rectangular  in  girdle  view  and  show  the  nodules  plainly. 
There  is  a  vast  number  of  species  and  varieties,  many  of 
which  are  very  common.  In  some  species  the  striae  can  be 
resolved  into  pearls.  These  are  the  Naviculae  proper.  In 
other  species  they  cannot  be  resolved,  and  the  valves  usually 
have  wide  rounded  ends.  These  were  formerly  set  apart  as  a 
separate  genus, — Pinnularia.  (PI.  I,  Figs.  7  and  8.) 

StauroneLs. 

Frustules  similar  to  those  of  Navicula.  Valves  symmetrical, 
possessing  a  straight  raphe,  with  medial  and  terminal  nodules. 
The  striae  are  pearled.  There  is  a  narrow  clear  space  along 
the  raphe  and  a  wider  transverse  clear  space  at  the  medial 
nodule  extending  to  the  sides  of  the  valve,  so  that  the  valves 
have  the  appearance  of  being  marked  with  a  cross.  A  number 
of  species  have  been  described,  but  in  some  instances  they  are 
very  similar  to  Navicula.  (PL  I,  Figs.  9  and  10.) 

Schizonema. 

Frustules  quite  similar  to  those  of  Navicula,  and  enclosed  in 
mucilaginous  tubes,  as  Encyonema.  Raphe  straight,  sometimes 
showing  a  double  line.  Striae  generally  parallel,  reaching  to 
the  raph6,  but  not  to  the  central  nodule,  around  which  there  is 
a  clear  space.  More  common  in  salt  water  than  in  fresh  water. 

Pleurosigma. 

Frustules  like  those  of  Navicula,  but  with  axis  turned  like  a 
letter  S.  Raphe  sigmoidal.  Striae  ornate,  pearled,  very  fine 
on  some  species.  Endochrome  in  two  layers.  (PI.  I,  Fig.  n.) 

FAMILY    GOMPHONEME^E. — Valves   cuneate  ;    central   nodule   un- 
equally distant  from  the  ends. 

Gomphonema. 

Frustules  borne  on  pedicels  more  or  less  branched.  Valves 
wedge-shaped,  with  more  or  less  undulating  margins  and 
rounded  ends.  A  central  nodule  near  the  large  end.  Raphe 
straight,  dividing  the  valve  symmetrically.  Striae  pearled, 
transverse,  radiating  slightly  about  the  nodules.  The  frustules 
seen  in  girdle  view  are  wedge-shaped,  with  straight  sides  and 


DIA  TO  MA  CEM.  1 8/ 

with  central  nodule  visible.  There  are  a  number  of  species, 
some  of  which  are  common.  (PL  I,  Fig.  12.) 

FAMILY  COCCONIDE^:. — Frustules  with  valves  unlike.  Valves 
broadly  oval. 

Cocconeis. 

Frustules  somewhat  arched  or  lens -shaped ;  in  valve  view, 
elliptical  or  discoidal.  Striae  have  a  general  direction  trans- 
verse to  the  axis,  but  the  convexity  of  the  frustules  gives  them 
the  appearance  of  inclining  towards  the  poles.  Upper  and 
lower  valves  dissimilar,  possessing  a  medial  nodule  and  raphe 
or  pseudo-raphe.  (PL  I,  Figs.  13  and  14.) 

TRIBE   II.     PSEUDO-RAPHIDIE^E. 

Possessing  a  false  raphe  (simple  line  or  blank  space)  on 
one  or  both  valves;  with  or  without  nodules.  Frustules 
generally  bacillar,  sometimes  oval  or  suborbicular,  without 
processes,  spines,  or  awns.  Synedra  Gaillonii  is  the  typical 
form. 

FAMILY  FRAGILARIE^E. — Frustules  adherent,  forming  a  ribbon-like, 
fan-like,  or  zigzag  filament,  or  attached  by  a  gelatinous  cushion  or 
stipe. 

Epithemia. 

Frustules  cymbiform,  symmetrical  with  respect  to  the  minor 
axis,  with  a  false  raphe  and  no  nodules.  Valves  marked  by 
lines  and  pearls  approximately  at  right  angles  to  the  major  axis, 
but  inclined  towards  the  end  of  the  frustule  on  the  convex 
side.  The  frustules  in  girdle  view  are  seen  to  be  somewhat 
inflated  at  the  centre.  There  are  several  species,  differing 
considerably  in  the  shape  of  the  valves.  (PL  I,  Figs.  15 
and  16.) 
Eunotia. 

Frustules  elongated,  symmetrical  with  respect  to  the  minor  axis. 
Occurring  singly,  free -swimming  or  attached.  Valves  arcuate, 
with  the  convex  side  undulated.  Transversely  striated,  with 
two  false  terminal  nodules  and  no  medial  line.  The  frustules 


1 88  THE   MICROSCOPY  OF  DRINKING-WATER. 

are  quadrangular  in  girdle  view.  There  are  but  few  species, 
the  most  common  being  the  E.  tridentula.  (PI.  I,  Fig.  17.) 

Himantidium. 

Sometimes  included  under  Eunotia.  The  frustules  differ  from 
Eunotia  by  remaining  attached  after  division,  forming  a  band 
as  in  Fragilaria  ;  by  having  the  convex  side  of  the  valve  entire 
instead  of  undulate ;  and  by  being  somewhat  bent  in  girdle 
view.  (PI.  II,  Figs,  i  and  2.) 

Asterionella. 

Frustules  long,  linear,  inflated  at  the  ends.  They  are  united 
by  their  extremities  into  stars  or  chains,  as  shown  in  the  girdle 
view.  The  typical  group  is  composed  of  8  frustules  sym- 
metrically and  radially  arranged.  Groups  of  4,  6,  or  7  are 
common.  When  rapidly  dividing  they  may  assume  a  spiral 
arrangement.  The  valves  are  very  finely  striated,  with  a 
straight  pseudo-raphe.  There  is  one  general  species,  the  A. 
formosa,  characterized  by  having  the  basal  end  of  the  frustules 
much  larger  than  the  free  end,  and  by  having  on  that  end  a 
larger  surface  in  contact  with  the  adjoining  frustules.  There 
are  several  varieties,  advanced  by  some  authors  to  the  rank  of 
species.  The  most  common  is  A.  formosa,  var.  gracillima. 
(PI.  II,  Figs.  3  to  7.) 

Synedra. 

Frustules  elongated,  straight  or  slightly  curved.  Valves  some- 
what dilated  at  the  centre  and  with  a  medial  line  or  false  raphe 
and  occasionally  false  nodules.  They  usually  have  straight  and 
almost,  but  not  quite,  parallel-sides.  They  are  finely  trans- 
versely striated.  There  are  several  common  species.  S. 
pulchella  has  lanceolate  valves,  with  ends  somewhat  attenuated. 
In  girdle  view  they  are  seen  to  be  attached  valve  to  valve  and 
present  the  appearance  of  a  long  band  or  a  fine-toothed  comb. 
S.  ulna  has  a  very  long  rectilinear  valve,  with  conspicuous 
transverse  striae.  There  is  a  false  raphe,  with  a  narrow  clear 
space.  They  are  often  free-floating.  S.  lanceolata  has  a  long 
thin  valve,  swollen  at  the  centre,  but  tapering  to  sharp  points 
at  the  ends.  S.  radians  has  straight  needle-like  valves.  They 
are  united  at  the  base  like  Asterionella,  but  the  frustules  do  not 
lie  in  the  same  plane.  (PL  II,  Figs.  8  to  n.) 


D I  A  TO  MA  CEsE.  1 8  9 

Fragilaria. 

Frustules  attached  side  by  side,  forming  bands  as  in  the  case  of 
Synedra  pulchella.  Valves  elongated,  straight,  with  ends 
lanceolate  or  slightly  rounded.  In  girdle  view  the  frustules 
are  rectangular  and  are  in  contact  with  each  other  through 
their  entire  length.  Valves  transversely  striated,  with  a  false 
raphe  scarcely  visible.  There  are  several  common  species. 
(PL  II,  Figs.  12  and  13.) 

Diatoma. 

Frustules  attached  by  their  angles  forming  zigzag  chains,  or 
rarely  in  bands.  In  girdle  view  they  are  quadrangular.  Valves 
elliptical-lanceolate,  with  transverse  ribs,  between  which  are 
fine  striae.  There  is  a  longitudinal  pseudo-raphe.  There  are 
two  common  species, — D.  vulgar e  and  D.  tenue.  (PI.  Ill, 
Figs,  i  to  3.) 

Meridion. 

Frustules  attached  valve  to  valve,  forming  curved  bands  seen 
as  fans,  circles,  or  spiral  bands.  The  frustules  are  wedge- 
shaped  in  girdle  view,  which  causes  the  peculiar  shape  of  the 
bands.  Valves  also  wedge-shaped,  with  somewhat  rounded 
ends ;  furnished  with  transverse  ribs,  between  which  are  fine 
striae.  Pseudo-raphe  indistinct.  There  is  one  principal 
species, — M.  circulare.  (PI.  Ill,  Figs.  4  and  5.) 

FAMILY  TABELLARIE^. — Frustules  with  internal  plates,  or  imperfect 
•septa,  often  forming  a  filament. 

Tabellaria. 

Frustules  square  or  rectangular  in  girdle  view,  attached  by 
their  corners  and  forming  zigzag  chains.  In  this  view  they  are 
seen  to  be  marked  with  longitudinal  dividing  plates,  which 
extend  from  the  ends  not  quite  to  the  middle  and  which  ter- 
minate in  rounded  points.  The  valves  are  long  and  thin,  and 
are  dilated  at  the  extremities  and  in  the  middle.  There  are 
fine  tranverse  striae  and  an  indistinct  pseudo-raphe.  The  endo- 
chrome  is  usually  in  rounded  lumps.  There  are  two  very  com- 
mon species,  —  T.  fenestrata  and  T.  flocculosa.  (PI.  Ill, 
Figs.  6  to  9.) 


1 90  THE   MICROSCOPY   OF  DRINKING-WATER. 

FAMILY     SURIRELLE^E. — Frustules  alate    or   carinate  ;     frequently 

cuneate. 

Nitzschia. 

Frustules  free,  single,  elongated,  linear,  slightly  arched,  or 
sigmoidal ;  with  a  longitudinal  keel  and  one  or  more  rows  of 
longitudinal  points.  Valves  finely  striated,  without  nodules. 
There  are  many  species.  (PI.  Ill,  Figs.  10  to  12.) 

Surirella. 

Frustules  free,  single,  furnished  with  alae  on  each  side.  A 
transverse  section  of  the  frustule  shows  a  double-concave  outline. 
Valves  oval  or  elliptical,  with  conspicuous  transverse  tubular 
striae,  or  canaliculi,  between  which  there  are  sometimes  very 
fine  pearled  strias.  There  is  a  wide  clear  space,  or  pseudo-raphe. 
The  frustules  are  sometimes  cuneate  in  girdle  view.  The 
valves  sometimes  have  a  warped  surface.  There  are  many 
common  species,  most  of  them  of  very  large  size.  (PL  III, 
Figs.  13  and  14.) 


TRIBE   III.     CRYPTO-RAPHIDIE^E. 

Never  possessing  a  raphe  or  a  false  raphe.  Frustules 
generally  circular  or  angular,  often  provided  with  teeth, 
spines,  or  processes.  Stephanodiscus  Niagara  is  the  typical 
form. 

FAMILY  MELOSIRE^E.  —Frustules  cylindrical,  adhering  and  forming 
a  stout  filament  ;  valves  circular,  sometimes  armed  with  spines. 

Melosira. 

Frustules  with  circular  valves  and  very  wide  connective  bands, 
attached  valve  to  valve  so  as  to  form  long  cylindrical  fila- 
ments. In  girdle  view  they  are  usually  rectangular,  though 
sometimes  with  rounded  ends  ;  at  the  centre  there  are  often 
conspicuous  constrictions.  The  girdles  are  often  marked  with 
dots.  The  valves  are  radially  striated,  with  a  clear  central 
space.  At  the  edge  there  is  often  a  keel  or  row  of  projecting 
points,  seen  in  girdle  view.  There  are  several  common  species. 
M.  granulata  is  the  most  common  free-floating  form,  and  M. 


DIA  TO  MA  CE&.  1 9 1 

variant,  the  most  common  filamentous  form.    (PI.  Ill,  Figs.  15 
to  17.) 
FAMILY  COSCINODISCE^E. — Valves  circular,  generally  with  radiating 

cellules,  granules,    or    puncta ;     sometimes    with    marginal   or   intra- 

marginal  spines  or  distinct  ribs  ;  without  distinct  processes.  . 

Cyclotella. 

Frustules  discoidal,  single,  occasionally  attached  valve  to  valve, 
but  never  forming  long  filaments.  Valves  circular,  finely 
marked  by  radial  striae.  'There  is  usually  an  outer  ring  of 
radial  lines,  inside  of  which  there  are  puncta  and  fine  dots 
somewhat  irregularly  arranged.  These  cannot  be  seen  with 
low  powers.  In  girdle  view  the  frustules  appear  rectangular 
or  somewhat  sigmoidal,  with  warped  valves,  as  in  C.  operculaia. 
They  are  often  of  very  small  size.  (PL  III,  Figs.  18  and  19.) 

Stephanodiscus. 

Frustules  discoidal,  single.  Valves  circular,  with  curved  sur- 
face, with  fringe  of  minute  marginal  teeth.  Striae  fine  radial. 
Frustules  rectangular  in  girdle  view,  showing  projection  of 
middle  of  valve.  Teeth  most  conspicuous  in  girdle  view. 
Endochrome  conspicuous,  in  rounded  lumps.  The  frustules 
are  often  of  considerable  size.  (PI.  Ill,  Figs.  20  and  21.) 


CHAPTER    XVL 
SCHIZOMYCETES. 

THE  Schizophyceae  comprise  those  vegetable  organisms  in 
which  the  chief  mode  of  propagation  is  that  of  cell-division. 
They  are  either  destitute  of  chlorophyll  or  contain  besides  the 
chlorophyll  a  coloring  substance  known  as  phycocyan  or 
phycochrome,  which  itself  may  be  a  modification  of  chloro- 
phyll. The  cells  have  a  somewhat  firm  cell-wall,  but  no 
nucleus. 

The  Schizophyceae  may  be  divided  into  two  classes, — the 
Schizomycetes  and  the  Cyanophyceae.  The  latter  contain 
chlorophyll,  but  the  former  do  not. 

Besides  the  bacteria,  which  are  not  described  in  this  work. 
there  are  but  four  genera  belonging  to  the  Schizomycetes 
that  are  of  interest  to  the  water-analyst.  They  are  so 
imperfectly  understood  that  no  satisfactory  classification  has 
been  suggested.  Some  authorities  include  them  among  the 
Fungi. 

iLeptothrix. 

Simple  filaments,  with  indistinct  or  no  articulation,  without 
oscillating  movement,  and  with  no  sulphur-granules.  There 
are  several  indistinct  species.  They  are  usually  colorless.  The 
aquatic  forms  occur  as  interwoven  masses  of  long  slender  fila- 
ments, the  diameter  of  which  varies  from  i  to  3  ju.  Lepto- 

192 


SCHIZOMYCETES.  193 

thrix  ochracea,  observed  in  driven  wells  where  the  water  con- 
tains much  iron,  is  generally  referred  to  the  genus  Crenothrix, 
but  its  relation  to  the  typical  form  of  Crenothrix  is  not  under- 
stood. Very  slender  forms  of  Oscillaria  are  liable  to  be  mis- 
taken for  Leptothrix.  (PL  IV,  Fig.  i.) 

Cladothrix. 

Fine  filaments  resembling  those  of  Leptothrix,  colorless,  usually 
indistinctly  articulated,  straight,  undulated,  or  twisted.  There 
are  several  stages  of  development,  giving  rise  to  cocci-,  vibrio-, 
spirochsetae-,  and  filamentous-forms.  The  special  characteristic 
of  the  genus  is  that  of  false  branching,  a  turning  aside  of 
single  portions  of  the  filaments  followed  by  subsequent  ter- 
minal growth.  There  are  several  indistinct  species.  The  most 
important  is  C.  dichotoma,  which  is  found  in  sewage  and  pol- 
luted water.  (PL  IV,  Fig.  2.) 

Beggiatoa. 

Threads  indistinctly  articulated,  colorless,  containing  numerous 
dark  sulphur-granules.  The  filaments  often  have  an  active 
oscillating  movement.  They  are  usually  short  and  from  i  to 
3  yu  in  diameter.  Sometimes  abundant  in  sulphur  springs. 
There  are  several  doubtful  species.  The  most  common  is  B. 
alba.  (PL  IV,  Fig.  3.) 

Crenothrix. 

Filaments  cylindrical,  transversely  divided  into  cells,  sur- 
rounded by  a  gelatinous  sheath  which  becomes  yellow  or 
yellowish-brown  through  deposits  of  iron  or  manganese.  Multi- 
plication takes  place  by  transverse  fission  and  occasionally 
by  longitudinal  fission.  Cells  also  escape  from  the  sheath  at 
the  end  or  side  and,  by  division,  form  new  filaments.  Repro- 
duction occurs  through  spores  formed  from  the  cells  within  the 
sheath.  There  is  one  principal  species,  C.  Kuhniana.  It 
occurs  in  single  filaments  or  in  brownish  tufts  or  mats,  often 
of  considerable  thickness.  The  filaments  are  i  ^  to  4  /*  thick, 
and  the  sheath  is  several  times  the  thickness  of  the  filaments. 
Articulation  is  distinct.  When  the  iron  of  the  sheath  is  dis- 
solved by  dilute  hydrochloric  acid  the  cells  appear  in  side 
view  as  distinct  rectangles,  each  one  somewhat  removed  from 
its  neighbor.  This  appearance  is  characteristic  of  Crenothrix. 


IQ4  THE   MICROSCOPY  OF  DRINKING-WATER. 

During  growth  the  cells  sometimes  push  themselves  forward 
in  the  sheath,  leaving  the  empty  sheath  behind.  The  older 
portion  of  the  sheath  is  darker  colored  than  the  growing  points. 
Crenothrix  occurs  chiefly  in  ground- waters  rich  in  organic 
matter,  iron  salts  nnd  carbonic  acid  and  deficient  in  oxygen. 
Its  growth  is  favored  by  darkness.  (PI.  IV,  Fig.  4.) 

Jackson  has  proposed  a  new  classification  of  this  genus, 
based  on  the  character  of  the  sheath-deposit.  C.  Kuhniana, 
which  deposits  iron,  he  maintains  ;  Leptothrix  ochracea,  which, 
deposits  alumina,  he  renames  C.  ochracea;  and  a  new  species,, 
which  deposits  manganese,  he  calls  C.  manganifera. 


CHAPTER    XVII. 
CYANOPHYCE^E. 

THE  plants  belonging  to  the  Cyanophyceae,  or  Phyco- 
chromophyceae,  are  characterized  by  the  presence  of  chloro- 
phyll plus  certain  coloring  substances  known  as  cyanophyll, 
phycocyanine,  phycoxanthine,  etc.,  which  are  probably 
modifications  of  chlorophyll;  by  the  absence  of  a  nucleus  and 
usually  of  starch-grains;  and  by  extremely  simple  but  imper- 
fectly understood  methods  of  reproduction.  The  plants  are 
one-  or  many-celled.  By  successive  division  of  the  cells  they 
are  very  commonly  associated  in  families  that  take  the  form 
of  filaments  or  of  spherical  or  irregular  masses. 

The  cell-wall  is  often  distinct  and  sharply  defined,  but  in 
some  cases  it  is  fused  with  a  gelatinous  mass  in  which  the 
cells  are  embedded.  This  gelatinous  matrix  is  more  common 
in  the  terrestrial  than  in  the  aquatic  species.  The  cell-con- 
tents are  usually  granular  and  homogeneous. 

The  color  varies  considerably  in  different  species  and 
under  different  conditions.  It  is  never  a  chlorophyll  green, 
but  ranges  from  a  color  approaching  that  to  a  blue-green, 
orange-yellow,  brown,  red,  or  violet.  The  coloring  matter 
known  as  phycocyanine  has  a  bluish  color  when  viewed  by 
transmitted  light,  and  a  reddish  color  when  viewed  by  re- 
flected light.  This  phenomenon  is  often  observed  in  ponds 
where  Cyanophyceae  are  abundant.  Looking  directly  at  the 

195 


196  THE   MICROSCOPY   OF  DRIN KING-WATER. 

pond  the  water  may  have  a  reddish-brown  color,  while  a  bottle 
filled  with  the  water  and  held  to  the  light  may  present  a  de- 
cidedly bluish-green  appearance.  This  is  particularly  true 
when  the  plants  have  begun  to  decay.  The  phycoxanthine 
is  said  to  have  a  yellowish  color.  The  liberation  of  the  gas- 
bubbles  from  some  species  seems  to  have  an  effect  on  the 
color  of  the  organisms.  Anabaena,  for  example,  may  have  a 
brownish-green  color  in  a  reservoir  and  a  very  light  blue- 
green  color  after  it  has  passed  through  the  pipes  of  a  dis- 
tribution system,  where  the  pressure  has  caused  the  gas  to 
be  expelled. 

The  Cyanophyceae  are  usually  separated  into  five  or  six 
groups,  which  are  ranked  by  different  writers  as  orders, 
families,  or  sections.  The  groups  are  here  considered  as 
families  belonging  to  two  orders. 

ORDER   I.     CYSTIPHOR^E. 

Unicellular  plants  with  spherical,  oblong,  or  cylindrical 
cells  enclosed  in  a  tegument  and  associated  in  families,  sur- 
rounded by  a  universal  tegument  or  immersed  in  a  generally 
colorless,  mucilaginous  substance  of  varying  consistency. 
Division  takes  place  in  one,  two,  or  three  directions,  the  cells 
after  division  usually  remaining  together  forming  an  amor- 
phous thallus.  It  is  probable  that  most  of  the  forms  belong- 
ing to  this  order  are  but  intermediate  stages  in  the  life-history 
of  plants  higher  in  the  scale  of  life.  There  is  but  one  family. 
It  contains  about  a  dozen  rather  imperfectly  defined  genera. 

FAMILY  CHROOCOCCACE^E. — Thallus   mucous  or  gelatinous,  amor- 
phous, enclosing  cells  and  families  irregularly  disposed. 

Chroococcus. 

Cells   spherical,   or   more  or  less  angular  from   compression, 
solitary  or  united  in  small  families.     Cell-membrane  thin  or 


C  YA  NOPH  YCEJE.  1 9  7 

confluent  in  a  more  or  less  firm  jelly.  Cell-contents  pale 
bluish-green,  rarely  yellowish.  Propagation  by  division  in 
three  directions.  Several  species  are  described.  Most  of 
them  are  terrestrial  and  not  aquatic.  The  most  common 
aquatic  species  are  C.  turgidus,  the  cells  of  which  are  from  10 
to  25  /<  in  diameter,  and  C.  cohcerens,  the  cells  of  which  are 
from  3  to  6  fj.  in  diameter.  (PL  IV,  Fig.  5.)  -' 

Gloeocapsa. 

Cells  spherical,  single  or  in  groups ;  each  cell  surrounded  by 
a  vesculiform  tegument  and  groups  of  cells  surrounded  by  an 
additional  tegument.  Cell-membrane  thick,  lamellated,  and 
sometimes  colored.  Division  in  three  directions.  Cell- 
contents  bluish-green,  brownish,  or  reddish.  There  are  many 
;i:i  described  species,  based  on  slight  distinctions  and  variations 
in  size  and  color.  Gloeocapsa  found  in  water  usually  has 
smaller  cells  and  a  more  distinct  tegument  than  Chroococcus. 
Comparatively  few  species  are  aquatic.  (PI.  IV,  Fig.  6.) 

Aphanocapsa. 

Cells  spherical,  with  a  thick,  soft,  colorless  tegument,  confluent 
in  a  homogeneous  mucous  stratum  which  is  sometimes  of  a 
brownish  color.  Cell-contents  bluish-green,  brownish,  etc. 
The  cells  divide  alternately  in  three  directions.  There  are 
several  species.  The  cells  vary  in  size  from  3  to  6  //.  (PI.  IV, 

Fig.  ?•) 
Microcystis. 

Cells  spherical,  numerous,  densely  aggregated,  enclosed  in  a 
very  thin,  globose  mother-vesicle,  forming  solid  families,  singly 
or  several  surrounded  by  a  universal  tegument.     Cell -contents 
aeruginous  to  yellowish-brown.     The  cells  divide  alternately  in 
three  directions.    This  genus  represents  a  condition  of  frequent 
occurrence    in   the   process  of  development  of  higher  forms 
There  are  several  indistinct  species  common  in  water.     The 
cells  vary  in  size  from  4  to  7  fi  in  diameter  and  the  colonies 
from  10  to  100  /*.      (PI.  IV,  Fig.  8.) 
Clathrocystis. 

Cells  very  numerous,  small,  spherical  or  oval,  aeruginous,  em- 
bedded in  a  colorless  matrix.  Multiplication  by  division  of 
the  cells  within  the  thallus.  The  thallus  is  at  first  solid,  then, 


198  THE   MICROSCOPY   OF  DRINKING-WATER. 

becomes  saccate  and  clathrate  (perforated)  ;  broken  fragments 
are  irregularly  lobed.  There  is  but  one  species, — C.  ceruginosa. 
The  cells  are  from  2  to  4  >u  in  diameter  and  the  thailus  from 
25  JJL  to  5  mm.  This  species  is  widely  distributed.  (PI.  IV, 

Fig.  9-) 
Ccelosphzerium. 

Cells  numerous,  minute,  globose  or  subglobose,  geminate, 
quaternate,  or  scattered,  immersed  in  a  mucous  stratum.  Cell- 
contents  aeruginous,  granulose.  The  thailus  is  globose,  vesic- 
ular, hollow,  the  cells  being  found  only  on  the  outer  surface. 
Multiplication  takes  place  by  division  of  the  cells  on  the  surface 
and  by  the  escape  and  further  development  of  certain  peri- 
pheral cells.  There  is  one  common  species,  C.  Kuetzingianum. 
The  cells  are  from  2  to  5  >w  in  diameter  and  the  thailus  from 
50  to  500  ;*.  (PI.  IV,  Fig.  10.) 

Merismopedia. 

Cells  globose  or  oblong,  seruginous  or  brownish,  with  confluent 
teguments.  Division  in  two  directions.  The  thailus  is  tabular, 
quadrate,  free-swimming,  the  cells  being  arranged  in  groups  of 
4,  8,  1 6,  32,  64,  128,  etc.  There  are  several  indistinct  species. 
The  diameter  of  the  cells  varies  from  3  to  7  >u.  (PL  IV, 
Fig.  ii.) 

Gloeothece. 

Similar  to  Gloeocapsa,  but  with  oblong  or  cylindrical,  instead 
of  spherical  cells.  Terrestrial  rather  than  aquatic. 

Aphanothece. 

Similar  to  Aphanocapsa,  but  with  oblong  instead  of  spherical 
cells. 

Tetrapedia. 

Cells  compressed,  quadrangular,  equilateral,  subdivided  into 
quadrate  or  cuneate  segments  or  rounded  lobes,  either  by  deep 
incisions  or  wide  angular  sinuses.  This  genus  is  of  doubtful 
value. 

ORDER   II.     NEMATOGEN^E. 

Multicellular  plants,   the  cells  of  which  dividing  in   one 
direction,  form  filaments,  often  enclosed  in  a  tubular  sheath. 


C  YA  NOPH  YCE^E.  1 99 

The  filaments  (trichomes)  may  be  either  simple  or  branched. 
There  are  five  families. 

FAMILY  NOSTOCACE^E. — Plants  composed  of  rounded  cells  loosely 
united  into  filaments,  or  trichomes,  and  sometimes  embedded  in 
jelly.  The  filaments  do  not  branch  and  never  terminate  in  a  hair- 
point.  They  sometimes  forms  large  masses.  There  are  three  kinds 
of  cells — ordinary  vegetative  cells,  joints,  or  articles ;  heterocysts  ;  and 
spores.  The  ordinary  cells  are  spherical,  elongated,  or  compressed. 
The  cell-contents  are  bluish -green  or  brownish,  and  are  usually  granular. 
The  heterocysts  are  cells  found  at  intervals  in  the  filaments.  They  are 
spherical,  elliptical,  or  elongated,  and  are  usually  somewhat  larger 
than  the  vegetative  cells.  Their  cell-contents  are  generally  clear  or 
very  finely  granular,  and  usually  of  a  light  bluish-green  color.  The 
cell-wall  is  sharply  defined,  and  there  are  two  polar  lumps  of  gelat- 
inous material  that  cause  them  to  adhere  to  the  adjoining  cells.  The 
function  of  the  heterocysts  is  unknown,  but  they  are  thought  to  be  in 
some  way  connected  with  the  process  of  reproduction.  The  spores  are 
usually  much  larger  than  the  vegetative  cells.  They  are  spherical, 
elliptical,  or  cylindrical.  Their  cell-contents  are  usually  very  granular 
and  dark-colored.  They  seem  to  be  more  highly  differentiated  than 
the  contents  of  the  vegetative  cells.  The  spores  are  heavy,  and  will 
sink  in  water  when  freed  from  the  filaments.  Multiplication  takes 
place  by  division  of  the  vegetative  cells,  by  means  of  the  spores,  and 
by  means  of  hormogons,  or  parts  of  the  internal  trichomes  which 
separate  from  the  filaments  and  form  new  plants.  The  character  and 
position  of  the  heterocysts  and  spores  form  the  chief  basis  for  the 
division  of  the  Nostocacese  into  genera.  The  classification  is  very 
indefinite. 
Nostoc. 

Cells  globose  or  elliptical ;  heterocysts  usually  globose  and 
somewhat  larger  than  the  vegetative  cells ;  spores  oval  and  but 
little  larger  than  the  heterocysts.  Spores  and  heterocysts  are 
both  intercalated  in  the  filaments,  rarely  terminal.  The  fila- 
•  .  ments  are  enclosed  in  a  gelatinous  envelope,  and  are  flexuously 
curved  and  irregularly  interwoven.  They  often  form  gelat- 
inous fronds  or  thalli  surrounded  by  a  firm  membrane.  The 
thalli  vary  in  diameter  and  are  sometimes  of  great  size.  There 


200  THE   MICROSCOPY   OF  DRINKING-WATER. 

are  many  species,  both  terrestrial  and  semi-aquatic.  The 
species  are  not  well  defined,  and  many  of  them  are  inter- 
mediate stages  in  the  life-history  of  higher  forms.  The  true 
Nostoc  is  seldom  found  in  drinking-water.  (PL  IV,  Fig.  12.) 

Anabrena. 

Vegetative  cells  spherical,  elliptical,  or  compressed  in  a 
quadrate  form.  Heterocysts  much  larger  than  the  vegetative 
cells,  subspherical,  elliptical,  or  barrel-shaped,  of  a  pale  yel- 
lowish-green color,  and  intercalated  in  the  filament.  Spores 
globose  or  oblong-cylindrical,  equal  to  or  somewhat  larger 
than  the  heterocysts,  rarely  smaller,  never  adjacent  to  the 
heterocyst.  The  filaments  are  moniliform ;  are  without 
sheaths  ;  are  straight,  curved,  circinate,  or  intertwined ;  have 
a  bluish-green  or  brownish  color ;  and  are  often  free-floating. 
There  are  several  important  but  imperfectly  defined  species. 
The  most  common  species  are  A .  flos-aquce  and  A .  circinalis. 
The  vegetative  cells  of  the  former  are  from  5  to  7  jn  in  diam- 
eter ;  those  of  the  latter  are  from  8  to  1 2  /i.  (PI.  IV,  Figs. 
13  and  14.) 

Sphaerozyga. 

Vegetative  cells  spherical,  elliptical,  or  transversely  com- 
pressed ;  of  a  bluish-green  or  brownish  color.  Heterocysts 
spherical  or  oval,  intercalated,  binary  or  solitary,  only  slightly 
larger  than  the  vegetative  cells.  Spores  on  each  side  of  and 
adjacent  to  the  heterocysts,  cylindrical,  with  rounded  ends, 
considerably  larger  than  the  heterocysts.  The  filaments  are 
moniliform ;  are  sheathless  or  covered  with  a  mucilaginous 
coating,  occasionally  agglutinated  in  a  gelatinous  stratum. 
There  are  several  species,  terrestrial  and  aquatic.  The  genus 
is  very  similar  to  Anabaena.  (PI.  V,  Fig.  i.) 

Cylindrospermum. 

Vegetative  cells  globose,  elliptical,  or  compressed,  homo- 
geneous or  granular.  Heterocysts  terminal,  spherical,  or  oval, 
but  little  larger  than  the  cells.  Spores  adjacent  to  the  het- 
erocysts, oval  or  cylindrical,  much  larger  than  the  cells.  The 
filaments  are  moniliform,  sheathless,  and  sometimes  taper 
slightly.  There  are  few  species,  and  these  resemble  some 
forms  of  Anabaena  and  Sphaerozyga.  (PI.  V,  Fig.  2.) 


C  YA  NOPH  YCE^E.  2  O I 

Aphanizomenon. 

Vegetative  cells  cylindrical,  closely  connected,  granular,  and 
with  little  color.  Heterocysts  rare,  intercalated,  oval,  but 
little  larger  in  diameter  than  the  cells.  Spores  very  rare, 
intercalated,  not  adjacent  to  heterocysts,  cylindrical,  with 
rounded  ends,  sometimes  of  dark  olive  color.  The  filaments 
are  cylindrical,  slightly  tapering,  and  densely  agglutinated  in 
fascicles,  occasionally  free.  The  fascicles  are  often  of  con- 
siderable size.  Diameter  of  filaments  4  to  6  //.  This  genus 
is  sometimes  mistaken  for  Oscillaria  or  Anabaena.  (PI.  V, 
Fig-  3-) 

FAMILY  OSCILLARIE^E  (LYNGBY^E). — Filaments  without  heterocysts 
or  spores,  with  or  without  sheath,  not  terminating  in  a  hair-point, 
single  or  associated  in  bundles  enclosed  in  a  common  sheath.  The 
division  of  the  filaments  into  cylindrical  cells  is  indistinct.  Mul- 
tiplication is  said  to  take  place  by  hormogons,  i.e.  parts  of  the 
trichomes  which  separate  from  the  rest  of  the  filament. 

Oscillaria. 

Cells  shortly  cylindrical,  disc-shaped  in  end-view,  closely 
united  into  a  simple,  branchless,  sheathless  filament.  The 
filaments  are  straight  or  somewhat  curved,  occasionally  fascic- 
ulate, and  have  rounded  ends.  The  color  is  bright  bluish- 
green,  steel-blue,  etc.  The  filaments  when  in  active  vegetative 
state  possess  characteristic  spontaneous  oscillating  movements. 
There  is  a  large  number  of  species,  that  vary  in  diameter  from 
i  to  50^,  and  have  cells  differing  in  shape  and  in  color. 
There  are  but  few  free-floating  forms.  (PI.  V,  Fig.  4.) 
Lyngbya. 

Filaments  enclosed  singly  in  a  sheath,  branchless,  but  with 
occasional  appearance  of  branching  during  multiplication, 
sometimes  combined  to  form  a  membranaceous  stratum.  Cells 
united  into  short  trichomes,  with  rounded  ends,  not  continuous 
in  the  sheath,  but  separated  by  clear  spaces.  Cell-contents 
blue-green,  granular.  Sheaths  pellucid,  hyaline.  Propagation 
is  said  to  take  place  by  hormogons  and  by  gonidia.  There 

are  many  species,  terrestrial  and  aquatic.      (PI.  V,  Fig.  5.) 

'  " 


2O2  THE   MICROSCOPY   OF  DRINKING- WATER. 

Microcoleus. 

Filaments  rigid,  articulate,  crowded  together  in  bundles,  en- 
closed in  a  common  mucous  sheath,  either  open  or  closed  at 
the  apex.  Sheath  ample,  colorless,  rarely  indistinct.  Several 
species,  chiefly  terrestrial.  (PL  V,  Fig.  6.) 

FAMILY  SCYTONEME/E. — Filaments  with  lateral  ramifications  (false 
branching)  in  which  some  of  the  cells  change  into  heterocysts  ; 
enclosed  in  a  sheath.  The  cells  divide  transversely.  The  ramifica- 
tions are  produced  by  the  deviation  of  the  trichome  and  emergence 
through  the  sheath.  The  branches  do  not  have  a  hair-point.  There 
are  several  genera. 

Scy  tonema. 

Sheath  enclosing  a  single  trichome,  composed  of  subspherical 
or  subcylindrical  cells,  with  scattered  heterocysts.  Color 
bluish-  or  yellowish-green.  Ramification  takes  place  by  a  fold- 
ing of  the  trichomes,  followed  by  rupture  of  the  sheath  and 
the  emergence  of  one  or  two  portions  of  the  folded  trichome 
at  right  angles  to  the  original  filament.  These  branched  fila- 
ments produce  interwoven  mats.  Multiplication  is  said  to  take 
place  by  microgonidia.  There  are  many  species,  terrestrial  and 
aquatic.  The  plant  is  not  found  free-floating.  (PL  V,  Fig.  7.) 

FAMILY  SIROSIPHONE^E. — Trichomes  enclosed  in  an  ample  sheath, 
profusely  branched.  Branches  are  formed  by  longitudinal  division 
•of  certain  cells  so  as  to  form  two  sister  cells,  the  inferior  of  which 
remains  a  part  of  the  trichome,  while  the  other,  by  repeated  division, 
grows  into  a  branch.  The  filaments  often  contain  3,  4,  or  more 
series  of  cells.  Propagation  is  said  to  take  place  by  means  of  micr-o- 
gonidia. 

Sirosiphon. 

Cells  one-,   two-,    or  many-seriate,   in  consequence   of  their 
lateral   division  or  multiplication.     The  cells  have  a  distinct 
membrane   and  the    sheaths  are   large.     The    plant    is  never 
found  free-floating.     (PL  V,  Fig.  8.) 
FAMILY  RIVULARIE^E.  — Filaments    free    or    agglutinated    into   a 

•definite    thallus,    terminating  at  the  apex  in  a  hair-like  extremity. 

Heterocysts   usually  basal.       Trichomes   articulated   like   Oscillaria, 


CYANOPHYCE&.  2O3 

parallel  or  radially  disposed.      Spores,  when  present,  cylindrical,  gen- 
erally adjacent  to  the  basal  heterocyst. 

Rivularia. 

Filaments  radial,  agglutinated  by  a  firm  mucilage,  and  forming 
well-defined  hemispherical  or  bladdery  forms.  Heterocysts 
basal.  No  spores  formed.  Ramifications  produced  by  trans- 
verse division  of  the  trichomes.  Color  greenish  to  brownish. 
Sheaths  usually  distinct.  Several  species,  terrestrial  and  aquatic. 
Occasionally  found  free-floating.  (PI.  V,  Fig.  9.) 


CHAPTER    XVIII. 
CHLOROPHYCE^E. 

THE  Algae  are  flowerless  plants  of  simple  cellular  structure, 
without  mycelia,  roots,  stems,  or  leaves.  The  functions  of 
the  plants  are  centred  in  the  individual  cells,  and  only  to  a 
limited  extent  is  there  any  " division  of  labor"  among  the 
cells. 

It  is  difficult  to  define  the  word  * 'Algae,"  because  it  is  used 
differently  by  different  writers.  In  the  broad  sense  it  includes 
all  of  the  thallophytes  which  contain  chlorophyll,  i.e.  the 
Diatomaceae,  Cyanophyceae,  Chlorophyceae,  Phaeophyceae, 
and  Rodophyceae.  This  is  the  older  meaning  of  the  term. 
It  is  used  in  contradistinction  to  the  Fungi,  which  contain  no 
chlorophyll.  In  the  narrower  sense  it  includes  only  the 
Chlorophyceae,  Phaeophyceae,  and  Rodophyceae.  This  is  the 
later  and  better  use  of  the  word.  The  Phaeophyceae  and 
Rodophycese  are  almost  entirely  marine  forms,  so  that,  as  far 
as  fresh-water  forms  are  concerned,  the  word  algae  is  almost 
synonymous  with  Chlorophyceae.  In  popular  speech,  how- 
ever, the  Cyanophyceae  are  frequently  spoken  of  as  the 
"blue-green  algae,"  and  the  diatoms  have  sometimes  been 
called  the  ''brown  algae." 

The  plants  belonging  to  the  Chlorophyceae  are  character- 
ized by  the  presence  of  true  chlorophyll,  a  nucleus,  starch- 
grains,  and  often  by  a  cell-wall  made  of  cellulose.  They  are 

204 


CHL  OROPH  YCEsE.  2O  5 

"*'  algae  "  in  the  strictest  sense  of  the  term.  They  cover  a 
great  range  of  complexity.  Some  of  them  are  minute,  uni- 
cellular forms  scarcely  distinguishable  from  the  Cyanophyceae; 
others  resemble  the  Protozoa;  while  others  are  large,  branch- 
ing, multicellular  forms  doubtfully  included  among  the  algae, 
^ind  very  similar  to  plants  much  higher  in  the  scale  of  life. 
Most  of  them  are  aquatic,  but  a  few  are  terrestrial.  Their 
color  is  almost  always  a  bright  chlorophyll  green,  but  occa- 
sionally it  is  yellowish-brown  or  even  a  bright  red.  The 
Chlorophyceae  increase  by  the  ordinary  processes  of  cell- 
division  observed  in  the  higher  forms  of  plant  life.  The  cells 
may  separate  after  division,  or  they  may  remain  associated  in 
colonies  or  in  simple  or  branching  filaments.  Reproduction 
takes  place  either  asexually,  i.e.  without  the  aid  of  fecunda- 
tion, or  sexually.  There  is  but  one  general  method  of  asexual 
reproduction,  namely,  the  formation  within  the  cell  of  spores, 
which  become  scattered  and  give  rise  to  new  cells.  There 
are  three  general  types  of  sexual  reproduction.  The  simplest 
is  the  formation  in  the  cells  of  zoospores,  which  become 
liberated  and  ultimately  copulate  with  other  zoospores.  Two 
of  these  zoospores  become  attached  by  their  ciliated  ends, 
their  contents  become  fused,  and  a  zygospore  results.  After 
a  period  of  rest  the  zygospore  may  develop  into  a  new  plant, 
or  may  break  up  into  other  spores.  The  second  type  of 
sexual  reproduction  is  known  as  conjugation.  Two  cells 
come  in  contact,  and  by  means  of  openings  in  the  cell-walls 
their  contents  become  fused.  A  zygospore  (sometimes  two) 
is  formed,  which,  after  a  period  of  rest,  gives  rise  to  new 
plants.  The  highest  form  of  sexual  reproduction  takes  place 
by  the  formation  of  a  rather  large  female  oospore,  which  be- 
comes fertilized  by  small  male  cells  or  spermatozoids.  This 
mode  of  reproduction  is  analogous  to  that  observed  in  the 


206  THE   MICROSCOPY   OF  DRINKING-WATER. 

higher  plants.  Many  of  the  Chlorophycese  exhibit  the  phe- 
nomenon of  ''alternation  of  generations,"  by  which  is  meant 
the  continued  propagation  of  the  plants  by  asexual  processes 
with  occasional  intervention  of  the  sexual  processes. 

ORDER    I.     PROTOCOCCOIDE^E. 

Unicellular  plants.  Cells  single  or  associated  in  families; 
tegument  involute  or  naked ;  no  branching  or  terminal  vege- 
tation. This  order  includes  many  of  the  free-floating  green 
algae  that  are  found  in  water. 

FAMILY  PALMELLACE.E. — Cells  solitary  or  in  families,  often  em- 
bedded in  a  jelly  and  forming  an  amorphous  stratum.  Multiplication. 
by  cell-division.  Reproduction  asexual,  by  active  gonidia. 

Gloeocystis. 

Cells  globose  or  oblong,  single  or  in  globose  families  of  2-4-8 
cells.  Common  and  individual  lamellose  gelatinous  integu- 
ments. Division  in  alternate  directions.  Reproduction  by 
zoogonidia.  There  are  several  species.  The  size  of  the  cells 
varies  from  2  to  12  ju  in  diameter  and  the  colonies  from  10  to 
100  JA.  Color  green,  sometimes  reddish.  Gelatinous  tegument 
colorless  or  ochraceous.  Usually  fixed,  sometimes  free-float- 
ing. (PI.  V,  Fig.  10.) 

Palmella. 

Cells  globose,  oval,  or  oblong,  surrounded  by  a  thick  confluent 
tegument ;  forming  an  amorphous  thallus.  Multiplication  by 
alternate  division  of  the  cells  in  all  directions.  An  uncertain 
genus.  Several  species,  usually  fixed.  Size  of  cells  varies 
from  i  to  15  /*.  Thallus  often  large.  Color  generally  green. 
(PI.  V,  Fig.  n.) 

Tetraspora. 

Cells  spherical  or  angular,  with  thick  teguments  confluent 
into  a  homogeneous  mucous  ;  forming  a  sac-like  thallus,  some- 
times of  large  size.  The  cells  divide  in  two  directions  and 
are  seen  normally  in  groups  of  four.  The  thalli  are  usually 
fixed,  but  the  quartettes  of  cells  are  sometimes  free-floating. 


CHLOROPHYCE&.  2O; 

Several  species,  all  green.  Cells  from  3  JJL  to  12  /<  in  diameter. 
(PI.  V,  Fig.  12.) 

Botryococcus. 

Cells  generally  oval,  with  a  thin  confluent  tegument,  densely 
packed,  forming  a  botryoid,  irregularly  lobed  thallus.  One 
species,  green,  free-floating,  with  cells  10  JA.  in  diameter.  (PI. 
VI,  Fig.  i.) 

Raphidium. 

Cells  fusiform  or  cylindrical,  straight  or  curved,  pointed  ends, 
occurring  singly,  in  pairs,  or  in  fascicles.  Cell-membrane  thin, 
smooth.  Cell-contents  green,  granular,  with  transparent  va- 
cuole.  Division  of  cells  in  one  direction.  There  are  several 
species,  with  numerous  varieties.  Two  species,  R.  polymor- 
phum  and  R.  convolutum,  are  common  free-floating  forms. 
The  latter  is  sometimes  known  by  the  name  Selenastrum. 
PL  VI,  Fig.  2.) 

Dictyosphseriurti. 

Cells  elliptical  or  kidney-shaped,  with  thick  mucous  invest- 
ment, more  or  less  confluent,  arranged  in  globose,  hollow 
families.  The  cells  are  connected  by  delicate  threads  radiating 
from  the  centre  of  the  colony  and  attached  to  the  concave  side 
of  the  cells.  The  threads  branch  dichotomously.  Division  in  all 
directions.  Two  or  three  species.  The  most  important  species 
is  D.  reniforme.  Color  green,  and  cells  6-10  X  10-20  //. 
(PI.  VI,  Fig.  3.) 

TMephrocytium. 

Cells  oblong,  kidney-shaped,  with  ample  tegument,  arranged 
in  free-swimming  colonies  of  2-4-8-16  cells.  Two  species. 
Green.  Cells  5  x  15  to  15  X  45  V-  (PL  VI,  Fig.  4.) 

Dimorphococcus. 

Cells  in  groups  of  four  on  short  branches,  the  two  intermediate 
contiguous  cells  oblique,  obtuse-ovate  ;  the  two  lateral,  opposite 
and  separate  from  each  other,  lunate.  In  colonies  with  cells 
connected  by  threads  radially  arranged  and  unbranched.  One 
free-floating  species.  Color  green.  Cells  5  to  10  /*  in  diam- 
eter. (PI.  VI,  Fig.  5,) 

FAMILY  PROTOCOCCACE^E. — Cells  solitary  or  forming  more  or  less 


208  THE   MICROSCOPY   OF  DRINKING-WATER. 

perfect  coenobia.     Propagation  by  asexual  zoospores  or  by  copulation 

of  zoogonidia.     In  general  there  is  no  vegetative  cell-division. 

Protococcus. 

Cells  spherical,  single  or  in  irregular  clusters.  Cell-membrane 
thin,  hyaline.  Cell-contents  green,  sometimes  reddish.  There 
is  but  one  species,  P.  vindis,  with  many  varieties.  Diameter 
of  cells  varies  from  3  to  50  JJL.  They  are  both  aquatic  and 
aerial.  Some  of  the  aquatic  forms  have  a  gelatinous  tegument 
and  are  called  Chlorococcus  by  some  writers.  The  distinction 
is  a  difficult  one  to  make.  (PI.  VI,  Fig.  6.) 

Polyedrium. 

Cells  single,  segregate,  free-swimming,  compressed,  3-4-8- 
angled.  Angles  sometimes  radially  elongated,  entire  or  bifid, 
rounded  at  the  ends.  Cell-membrane  thin,  even.  Cell-con- 
tents green,  granular,  sometimes  with  oil-globules.  Propaga- 
tion by  gonidia.  There  are  several  species.  One  of  the  most 
common  is  P.  longispinum.  (PI.  VI,  Fig.  7.) 

Scenedesmus. 

Cells  elliptical,  oblong,  or  cylindrical,  with  equal  or  unequal 
ends,  often  produced  into  a  spine-like  horn ;  usually  laterally 
united,  forming  coenobia.  Cell-contents  green.  Propagation 
by  segmentation  of  cell-contents  into  brood  families,  set  free 
by  rupture  of  the  maternal  cell-membrane.  There  are  several 
common  species,  S.  caudatus,  with  several  varieties,  S.  obtusus, 
and  S.  dimorphous.  The  cells  are  usually  2  or  3  ^  in  diam- 
eter and  from  8  to  25  jn  long.  (PI.  VI,  Fig.  8.) 

Hydrodictyon. 

Cells  oblong-cylindrical,  united  at  the  ends  into  a  reticulated, 
saccate  ccenobium.  Cell-contents  green.  Propagation  by 
macrogonidia  which  join  themselves  into  a  ccenobium  within 
the  mother  cell,  and  by  ciliated  microgonidia  which  copulate 
and  form  a  resting-spore.  One  species,  H.  utriculatum. 
Aquatic  and  attached.  (PI.  VI,  Fig.  9.) 

Ophiocytium. 

Cells  cylindrical,  elongated,  curved,  or  circinate,  one  end  and 
occasionally  both  ends  attenuated.  Cell-contents  green. 
Propagation  by  zoogonidia.  There  are  several  species.  The 
most  common  is  O.  cochleare,  the  cells  of  which  are  from 


CHL  OROPH 


209 


5  to  8  /i  in  diameter  and  of  various  lengths.     (PI.  VI,  Fig. 

10.) 
f*ed  last  rum. 

Cells  united  into  a  plane,  discoid  or  stellate,  free-swimming 
ccenobium,  which  is  continuous,  or  with  the  cells  interrupted 
in  a  perforate  or  clathrate  manner.  The  central  cells  are 
polygonal  and  entire ;  those  of  the  periphery  entire,  bi-lobed, 
with  lobes  sometimes  pointed.  Cell-contents  green,  granular. 
Propagation  by  macrogonidia  formed  within  the  cells,  which 
after  their  escape  divide,  arrange  themselves  in  a  single  layer, 
and  reproduce  the  form  of  the  mother  plant.  There  are 
several  species.  The  most  common  are  P.  Boryanum  and  P. 
simplex.  (PI.  VI,  Fig.  n.) 

Sorastrum. 

Cells  wedge-shaped,  compressed,  sinuate,  emarginate,  or  bifid 
at  the  apex ;  radially  disposed,  forming  a  globose,  solid,  free- 
swimming  coenobium.  There  is  but  one  species,  S.  spinulosum. 
The  cells  are  spined.  They  vary  in  size  from  12  to  20  //. 
The  coenobia  vary  in  diameter  from  25  to  75  /*.  (PI.  VI, 
Fig.  12.) 

Coelastrum. 

Cells  globose,  or  polygonal  from  pressure,  forming  a  globose, 
hollow  ccenobium,  reticulately  pierced.  The  cells  are  arranged 
in  a  single  layer,  sometimes  joined  by  radial  gelatinous  cords. 
Cell-contents  green.  Propagation  by  macrospores.  There  are 
several  species.  The  most  common  is  C.  microporum,  which 
has  8-16-32  cells,  and  the  diameter  of  which  varies  from  40  to 
100  p.  (PI.  VII,  Fig.  i.) 

Staurogenia. 

Cells  oblong-oval,  subquadrate,  or  rhomboidal,  arranged  in 
groups  of  4-8-16,  forming  a  cubical  ccenobium,  hollow  within. 
Cell-contents  green.  Propagation  by  quiescent  gonidia.  (PI. 
VII,  Fig.  2.) 

ORDER   II.     VOLVOCINIEiE. 

Unicellular    plants    occurring    as    mobile,    globose,    sub- 
globose,    or   flattened    quadrangular    ccenobia    composed    of 


210  THE   MICROSCOPY    OF  D R  INKING WATER. 

bi-ciliated  green  cells  which  are  more  or  less  spherical  or  com- 
pressed. The  ccenobia  as  a  whole  are  motile  because  of  the 
ciliated  cells,  and  hence  are  free-floating.  The  ccenobium 
sometimes  has  an  ample  hyaline  tegument.  Cell-contents 
green.  Propagation  sexual  or  asexual.  Asexual  propaga- 
tion takes  place  by  subdivision  of  the  larger  vegetative 
cells  into  new  families,  which  separate  from  the  mother  cell 
when  sufficiently  developed.  Sexual  propagation  takes  place 
by  means  of  female  spore-cells,  or  oospores,  developed  from 
the  vegetative  cells,  which  are  fertilized  by  antheridia  devel- 
oped from  other  vegetative  cells.  The  antheridia,  after 
escaping  from  the  cell  in  which  they  are  formed,  perforate 
the  membrane  of  the  oogonia,  after  which  the  oospore  goes 
into  a  resting  state  to  germinate  later.  This  order  is 
frequently  referred  by  zoologists  to  the  Protozoa. 

FAMILY  VOLVOCACE^E. — Characteristics  the  same  as  for  the  order, 

Volvox. 

Large  coenobium,  continually  rotating  and  moving,  looking 
like  a  hollow  globe  composed  of  very  numerous  cells  (several 
thousand)  arranged  on  the  periphery  at  regular  distances,  con- 
nected by  a  matrical  gelatin  which  has  the  appearance  of  a 
membrane  in  which  the  cells  are  embedded.  Cells  globose, 
bearing  two  cilia  that  extend  beyond  the  gelatinous  envelope. 
By  the  waving  of  these  cilia  the  colony  is  kept  in  motion. 
Cell-contents  green  ;  starch -granules  and  often  a  red  pigment- 
spot  present.  With  a  high  power  the  cells  are  seen  to  be  con- 
nected to  each  other  in  a  hexagonal  manner  by  fine  threads. 
Propagation  sexual  and  asexual,  as  described  under  the  order. 
The  oospores  and  antheridia  are  enclosed  in  flask-like  cells 
extending  inward.  The  spermatozoids  are  spindle-shaped  and 
furnished  with  two  cilia.  The  resting-spores  usually  produce 
eight  zoogonidia.  Asexual  propagation  takes  place  by  division 
of  the  larger  and  darker  flask-like  cells.  These,  usually  eight 
in  number,  develop  young  volvoxes  in  the  mother  cells.  They 


CHL  OR  OPH  YCE^?.  2  I  I 

are  very  conspicuous.  The  mother  cell  splits  along  well- 
defined  lines  and  the  young  forms  are  set  free.  There  is  practi- 
cally but  one  species,  V.  globator.  The  ccenobia  are  often 
one  millimeter  in  diameter.  (PL  VII,  Fig.  3.) 

Eudorina, 

Ccenobium  oval  or  spherical,  involved  in  a  gelatinous  mucilag- 
inous tegument,  composed  of  16-32  cells  arranged  around 
the  colorless  sphere  at  equal  distances.  The  ccenobium  is 
often  seen  moving  with  a  rolling  motion.  Cells  globose,  with 
two  protruding  cilia.  Cell-contents  green,  sometimes  with  a 
red  pigment- spot.  Asexual  propagation  takes  place  by  the 
division  of  the  cells  into  16-32  parts,  each  of  which  produces  a 
new  coenobium.  Sexual  propagation  as  described  for  the 
order.  Usually  four  of  the  thirty-two  cells  produce  antheridia, 
the  others  oogonia.  The  spermatozoids  are  pear-shaped  and 
are  bi -ciliated.  There  are  but  two  species,  E.  elegant,  and  E. 
stagnate.  The  cells  vary  from  5  to  25  //,  and  the  ccenobia 
from  25  to  150  /^,  in  diameter.  (PI.  VII,  Fig.  4.) 

Pandorina. 

Coenobium  globose,  invested  by  a  broad,  colorless,  gelatinous 
tegument,  composed  of  8  to  64  cells  crowded  together  or 
aggregated  in  a  botryoidal  manner.  (In  this  respect  it  differs 
from  Eudorina. )  Cells  green,  globose  or  polygonal  from  com- 
pression, bi -ciliated,  occasionally  with  a  red  pigment-spot. 
Sexual  propagation  takes  place  by  the  conjugation  of  zoospores 
produced  in  the  cells  of  the  coenobium,  which  after  union  give 
rise  to  resting-spores.  Asexual  propagation  takes  place  by  cell- 
division.  There  is  but  one  species,  P.  morum.  The  coenobium 
is  about  200  ju  in  diameter  and  the  cells  from  10  to  15  ju. 
(PI  VII,  Fig.  5.) 

Gonium. 

Ccenobium  quadrangular,  tabular,  with  rounded  angles,  formed 
from  a  single  flat  stratum  of  cells,  girt  by  a  broad,  hyaline, 
plane-convex  tegument.  Cells  16  (4  central  and  12  per- 
ipheral), polygonal,  connected  by  produced  angles,  and  fur- 
nished with  two  cilia.  Cell-contents  green.  Asexual  propaga- 
tion by  division.  Sexual  propagation  unknown.  There  is 


212  THE  MICROSCOPY   OF  DRINKING  WATER. 

but  one  species,  G.  pec  for  ale.     The  genus  is  an  uncertain  one. 
(PI.  VII,  Fig.  6.) 

ORDER   III.     CONJUGATE. 

Unicellular  or  multicellular  plants.  The  multicellular 
forms  have  no  terminal  vegetation  and  are  destitute  of  true 
branches.  The  chlorophyll  masses  are  arranged  in  plates, 
bands,  or  stellate  masses.  Starch-grains  are  abundant.  Mul- 
tiplication by  division  in  one  direction.  Reproduction  by 
zygospores  resulting  from  copulation  and  conjugation  of  two 
cells,  or  by  azygospores  formed  without  copulation.  There 
are  two  families  that  are  very  different  in  their  general  char- 
acteristics, but  that  agree  in  their  mode  of  reproduction. 

FAMILY  DESMIDIE^E. — The  Desmidieae,  or  Desmids,  form  a  large, 
well-defined  group  of  unicellular  algae.  They  are  characterized  by  two 
peculiar  features, — by  an  apparent  division  of  the  cell  into  two 
symmetrical  halves,  and  by  the  presence  of  projections  from  the  sur- 
face, either  inconspicuous  or  prolonged  into  spines.  The  cells  are  of 
various  sizes  and  forms,  often  curious  or  ornamental,  single  or  joined 
together  forming  a  filament.  The  transverse  constriction  is  sometimes 
•deep,  sometimes  slight,  and  occasionally  absent.  The  cell-wall  is  firm, 
almost  horny.  Some  writers  have  imagined  that  it  was  slightly  silic- 
ified.  The  cell  is  surrounded  by  a  mucous  covering  and  sometimes  by 
a  layer  of  gelatin.  The  cell-contents  are  green  and  granular.  Starch- 
grains  are  numerous.  At  the  ends  of  some  of  the  cells  there  are  clear 
spaces  in  which  are  seen  granules  that  occasionally  have  a  vibratory 
movement.  Cyclosis,  or  a  circulation  of  granules  in  the  watery  fluid 
next  the  cell-wall,  may  be  observed  in  some  species.  Some  species  of 
desmids  exhibit  voluntary  movements  of  the  entire  cell.  Closterium, 
for  example,  shows  certain  oscillations  and  backward  and  forward 
gliding  movements,  supposed  to  be  due  to  the  secretion  of  threads  of 
mucous.  Multiplication  takes  place  by  cell-division  and  by  conjuga- 
tion. In  the  first  case  the  two  halves  of  the  cell  stretch  apart  and 
become  separated  by  a  transverse  partition  ;  new  halves  ultimately 
form  on  each  of  the  original  halves,  so  that  two  symmetrical  cells 


CHL  OROPH  YCEJE.  2  I  3 

result.  These  afterwards  separate.  (See  PL  VIII,  Fig.  A.)  Sexual 
propagation  by  conjugation  takes  place  as  follows  :  Two  cells  approach 
and  each  sends  out  a  tube  from  its  centre.  These  tubes  meet,  swell 
hemispherically,  and,  by  the  disappearance  of  the  separating  wall, 
become  united  into  a  rounded  zygospore  with  a  thick  tegument  and 
sometimes  with  bristling  projections.  This  zygospore,  after  a  period 
of  rest,  loses  its  contents  through  a  rent  in  the  wall,  and  a  new  cell  is 
formed  which  ultimately  becomes  constricted  and  assumes  the  shape  of 
the  parent  cell.  (See  PI.  VIII,  Figs.  B  to  F.) 

Some  of  the  common  genera  are  described  below.     The  enormous 
number  of  species  makes  a  detailed  analysis  impracticable. 
Penium. 

Cells  straight,  cylindrical  or  fusiform,  not  incised  nor  con- 
stricted in  the  middle ;  ends  rounded.  Chlorophyll  lamina 
axillary  ;  containing  starch-granules.  Cell-membrane  smooth, 
finely  granulated,  or  longitudinally  striated.  Individuals  free- 
swimming  or  associated  in  gelatinous  masses.  (PI.  VII, 

Fig.  7-) 
Closterium. 

Cells  simple,  elongated,  lunate  or  crescent-shaped,  entire,  not 
constricted  at  the  centre.  Cell-wall  thin,  smooth  or  somewhat 
striated.  The  chlorophyllaceous  masses  are  generally  arranged 
in  longitudinal  laminae,  interrupted  in  the  middle  by  a  pale 
transverse  band.  At  each  end  there  is  a  clear,  colorless,  or 
yellowish  vacuole  in  which  minute  "dancing  granules"  may 
be  seen.  (PI.  VII,  Figs.  8  to  10.) 

Docidium. 

Cells  straight,  cylindrical  or  fusiform,  elongated,  constricted  at 
the  middle.  The  semi-cells  are  somewhat  inflated  at  the  base 
and  are  often  separated  by  a  suture.  Ends  rounded,  trun- 
cated or  divided.  Transverse  section  circular.  The  chloro- 
phyllaceous cytioplasm  has  a  parietal  or  axillary  arrangement. 
Terminal  vacuoles  with  ' '  dancing  granules  ' '  are  observed  in 
some  species.  (PL  VII,  Fig.  n.) 

Cosmarium. 

Cells  oblong,  cylindrical,  elliptical,  or  orbicular,  with  margins 
smooth,  dentate,  or  crenate  ;  deeply  constricted  j  ends  rounded 
or  truncate  and  entire ;  end  view  oblong  or  oval.  Chloro- 


214  THE  MICROSCOPY  OF  DRINKING-WATER. 

phyll  masses  parietal  or  concentrated  in  the  centre  of  the  semi- 
cells.  Cell- walls  smooth,  punctate,  warty,  or  rarely  spinous. 
The  zygospore  is  spherical,  tuberculated  or  spinous.  (PI.  VII, 
Fig.  12,  and  PI.  VIII,  Figs.  A  to  F.) 

Tetmemorus. 

Cells  cylindrical  or  fusiform,  slightly  constricted  in  the  middle, 
narrowly  incised  at  each  end,  but  otherwise  entire.  Cell-wall 
punctate  or  granulate.  (PI.  VII,  Fig.  13.) 

Xanthidi'im. 

Oils  single  or  geminately  concatenate,  inflated,  very  deeply 
constricted;  semi-cells  compressed,  entire,  spinous,  protrud- 
ing in  the  centre  as  a  rounded,  truncate,  or  denticulate  tubercle. 
Cell-wall  firm,  armed  with  simple  or  divided  spines.  The 
zygospores  are  globose,  smooth  or  spinous.  (PI.  VIII,  Figs, 
i  and  2.) 

Arthrodesmus. 

Cells  simple,  compressed,  deeply  constricted ;  semi-cells 
broader  than  long,  with  a  single  spine  on  each  side,  but 
otherwise  smooth  and  entire.  (PI.  VIII,  Fig.  3.) 

Euastrum. 

Cells  oblong  or  elliptical,  deeply  constricted ;  semi -cells 
emarginate  and  usually  incised  at  their  ends;  sides  sym- 
metrically sinuate  or  lobed,  provided  with  circular  inflated 
protuberances ;  viewed  from  the  vertex,  elliptical.  The  zygo- 
spores are  spherical,  tuberculose  or  spinous.  (PI.  VIII, 

Fig.  4.) 
Micrasterias. 

Cells  simple,  lenticular,  deeply  constricted  ;  viewed  from  front, 
orbicular  or  broadly  elliptical ;  viewed  from  the  vertex,  fusi- 
form, with  acute  ends  ;  semi-cells  three-  or  five-lobed  ;  lateral 
lobes  entire  or  incised ;  end  lobes  sinuate  or  emarginate  and 
sometimes  with  angles  bifid  or  produced.  (PI.  VIII,  Fig.  5.) 
Staurastrum. 

Cells  somewhat  similar  to  those  of  Cosmarium  in  front  view, 
but  angular  in  end  view ;  angles  obtuse,  acute,  or  drawn  out 
into  horn-like  processes.  Cell-wall  smooth,  punctate  or  gran- 
ular, hairy,  spinulose,  or  extended  into  arms  or  hair-like  proc- 
esses. Chlorophyll  masses  concentrated  at  the  centre  of  the 


CHLOROPHYCE^E.  2  I  5 

semi-cells,  with  radiating  margins.  The  zygospores  are  spined. 
(PI.  VIII,  Figs.  6  and  7.) 

Hyalotheca. 

Cells  short,  cylindrical,  usually  with  a  slight  obtuse  constric- 
tion in  the  middle ;  circular  in  end  view.  The  cells  are 
closely  united  into  long  filaments,  enclosed  in  an  ample,  color- 
less mucous  sheath.  The  chlorophyll  is  concentrated  in  a 
mass  which,  in  end  view,  has  a  radiate  appearance.  (PI.  IX, 
Fig.  i.) 

Desmidium. 

Cells  oblong-tabulate,  somewhat  incised ;  in  end  view,  tri- 
angular or  quadrangular;  united  intD  somewhat  fragile  fila- 
ments and  surrounded  by  a  colorless  mucous  sheath.  Chloro- 
phyll masses  in  each  semi-cell  concentrated  and  radiate  to  the 
angles.  Zygospores  smooth,  globose  or  oblong.  (PI.  IX, 

Fig.    2.) 

Sphaerozosma. 

Cells  bi-lobed,  elliptical,  or  compressed,  deeply  incised,  form- 
ing filaments  which  are  almost  moniliform  or  pinnatifid,  sur- 
rounded by  a  colorless  or  mucous  sheath.  Chlorophyll  mass 
concentrated,  somewhat  radiate.  (PL  IX,  Fig.  3.) 

FAMILY  ZYGNEMACE^E. — Multicellular  plants,  composed  of  cyMn- 
drical  cells  joined  into  filaments  and  forming  an  articulated  simple 
thread.  Cell-wall  lamellose.  Chlorophyll  arranged  as  twin  stellate 
nuclei,  as  axillary  laminae,  or  as  spiral  bands.  Starch -grains,  etc., 
conspicuous.  Propagation  by  zygospores  resulting  from  copulation, 
which  takes  place  by  the  union  of  two  filaments.  The  filaments  come 
into  proximity,  the  cells  put  out  short  processes^  which  unite?  forming 
tubular  passages  between  pairs  of  cells.  Through  these  connecting 
tubes  the  cell-contents  of  one  cell  passes  into  and  unites  with  the  cell- 
contents  of  another.  This  results  in  the  formation  of  a  zygospore 
often  clothed  with  a  triple  membrane.  Copulation  is  said  to  be 
scalariform  when  opposite  cells  of  two  filaments  unite  by  ladder-like 
tubes,  geniculate  when  the  cells  become  bent  and  unite  at  the  angles, 
and  lateral  when  the  process  takes  place  between  two  adjoining  cells 
of  the  same  filament.  The  family  is  sometimes  divided  into  two  sec- 
tions, the  Zygnemina  and  Mesocarpince.  In  the  second  section  the 


2l6  THE   MICROSCOPY   OF  DRINKING-WATER. 

spore  formed  is  not  a  true  zygospore.  It  is  formed  by  a  flowing  to- 
gether of  only  a  part  of  the  cell-contents.  The  zygospores  germinate 
by  putting  forth  a  single  germ,  which  elongates  by  transverse  division 
into  a  filament. 

Spirogyra. 

Cells  cylindrical,  sometimes  replicate,  or  folded  in  at  the  ends. 
Chlorophyll  arranged  in  one  or  several  parietal  spiral  bands 
winding  to  the  right.  Copulation  scalariform,  sometimes 
lateral.  Copulating  cells  often  shorter  than  sterile  ones  and 
more  or  less  swollen.  Zygospores  always  within  the  wall  of 
one  of  the  united  cells.  There  are  very  many  species,  differ- 
ing in  size  of  cells,  number  and  arrangement  of  spirals,  repli- 
cation at  the  end  of  cells,  character  of  the  zygospore,  etc- 
(PI.  IX,  Figs.  4  and  5.) 

Zygnema. 

Cells  with  two-axil,  many-rayed  chlorophyll  bodies  near  the 
central  cell-nucleus,  containing  one  or  more  starch-granules. 
Copulation  scalariform  or  lateral.  Zygospore  in  one  of  the 
united  cells.  (PI.  IX,  Fig.  6.) 

Zygogonium. 

Like  Zygnema,  except  that  the  zygospores  are  located  in  the 
connecting  tube  between  the  united  cells. 


ORDER   IV.     SIPHONED. 

Unicellular  plants  when  in  the  vegetative  state;  cells 
tubular  or  utricle-shaped,  often  branched.  Cell-contents 
green,  granular.  Propagation  by  sexual  fertilization,  asexual 
zoospores,  or  by  microgonidia. 

FAMILY  VAUCHERIACE^E. — Plants  consisting  of  elongated,  robust 
tubular  filaments,  more  or  less  branched,  growing  in  tufts.  Chloro- 
phyll granules  are  evenly  distributed  on  the  inside  walls  of  the  cells, 
and  starch-grains  and  oil-globules  are  conspicuous.  Sexual  propaga- 
tion takes  place  by  means  of  oospores  fertilized  by  spermatozoids. 
The  oogonia  are  lateral,  sessile,  or  borne  on  a  simple  pedicel;  the 
antheridia  usually  develop  on  the  same  filament.  Asexual  propaga- 


CHL  OROPH  YCE^.  2  I  / 

tion  takes  place  by  means  of  zoospores  produced  in  a  terminal 
sporangium.  The  zoospores  are  ciliated,  but  go  through  a  resting 
period  before  germinating.  Propagation  also  takes  place  by  means 
of  microgonidia  produced  in  the  vegetative  cells. 

Vaucheria. 

The  characteristics  are  described  under  the  family.  There  are 
many  species,  aquatic  and  terrestrial.  (PI.  IX,  Fig.  7.) 

ORDER  V.     CONFERVOIDE^E   (NEMATOPHYCE^E). 

Multicellular  plants  consisting  of  simple  or  branched 
filaments  forming  articulated  threads  or  membranaceous 
thalli.  Vegetation  terminal,  sometimes  lateral.  Propagation 
by  oospores  fertilized  by  spermatozoids,  or  by  copulation  of 
zoogonidia.  In  many  of  the  genera  the  method  of  propaga- 
tion is  not  well  known.  The  order  contains  a  great  variety 
of  forms,  and  various  methods  of  classification  have  been 
adopted  by  different  writers.  There  are  but  few  genera  that 
interest  the  water-analyst 

FAMILY  CONFERVACE^E. — Plants  consisting  of  simple  or  branched 
filaments,  with  terminal  vegetation,  composed  of  elongated,  cylindri- 
cal cells,  rarely  abbreviated  or  swollen.  Cell-membrane  sometimes 
lamellose.  Vegetation  by  division  in  one  direction.  Propagation  by 
zoospores. 

Conferva. 

Articulate  threads  simple ;  cells  cylindrical,  sometimes 
swollen  ;  chlorophyll  homogeneous.  Vegetation  by  division. 
Propagation  by  zoogonidia.  There  are  many  common  species, 
varying  greatly  in  diameter  of  filaments.  Many  vegetative 
filaments  of  other  plants  are  liable  to  be  mistaken  for  Conferva. 
The  characteristics  of  the  genus  are  somewhat  vague.  (PI. 
IX,  Fig.  8.) 
Cladophora. 

Articulate  threads  very  much  branched,  the  branched  cells 
being  much  thinner  than  the  primary  cells.  Cell-membrane 
thick,  lamellose.  Cells  cylindrical,  somewhat  swollen.  Cell- 


2  I  8  THE   MICROSCOP  Y   OF  DRINKING-  WA  TER. 

contents  green,  containing  many  starch-granules.  Propagation 
by  zoogonidia,  which  develop  in  large  numbers.  (PI.  IX, 
Fig.  9-) 

FAMILY  CEDOGONIACE^E.  —  Filaments  articulated,  simple  or 
branched.  Cells  cylindrical,  terminal  cells  sometimes  setiform. 
Propagation  by  asexual  zoospores  or  by  oospores  sexually  fertilized. 
Plants  monoecious  or  dioecious ;  when  dioecious  the  male  plants  are 
either  dwarf,  i.e.  produced  from  short  cells  of  the  female  plants,  or 
elongated  and  independent.  There  are  two  genera,  (Edogonium  and 
Bulbochaete,  each  with  many  species. 

FAMILY  ULOTRICHE^E. — Filaments  shortly  articulate,  simple,  free, 
sometimes  laterally  connate  in  bands.  Cell-membrane  thick  and 
lamellose.  Cell-contents  at  first  effused,  after  division  transmuted 
into  gonidia.  Propagation  by  ciliated  macrospores  which  do  not 
-copulate,  or  by  microzoospores  which  do  or  do  not  copulate. 

Ulothrix. 

Filaments  simple,  articulate.  Articulations  usually  shorter 
than  their  diameter.  Cell-membrane  thin.  Cell-contents 
green,  effused  or  parietal,  enclosing  amylaceous  granules. 
Propagation  by  macro-  and  micro-zoospores.  Several  common 
species.  (PI.  IX,  Fig.  10.) 

FAMILY  CH^ETOPHORACE^E. — Filaments  articulate,  dichotomously 
or  fasciculately  branched,  accumulated  in  tufts  in  a  gelatinous  mucus, 
or  constituting  a  filamentose  or  foliaceous  thallus.  Propagation  by 
oospores  sexually  fertilized,  or  by  zoogonidia.  Monoecious  or 
dioecious. 
Stigeoclonium. 

Filaments  articulate,  with  simple  scattered  branches.  Branches 
similar  to  the  stems,  attenuated  into  a  colorless  bristle.  Cell- 
membrane  thin,  hyaline.  Cell -contents  green,  with  chloro- 
phyll arranged  in  transverse  bands.  Propagation  by  oospores 
or  zoogonidia.  (PI.  X,  Fig.  i.) 
Draparnaldia. 

Filaments  articulate,  much  branched ;  the  main  stem  com- 
paratively thick,  composed  of  large,  mostly  hyaline  cells,  with 
broad,  transverse  chlorophyll  bands.  Many  branches  and  sub- 


CHLOROPHYCE&,  2 1 9 

branches,  alternate  or  opposite.  The  terminal  cells  ->re 
empty,  hyaline,  and  often  elongated  into  a  bristle.  The 
branch  cells  only  are  fertile.  The  plant  is  enveloped  in  a 
gelatinous  covering.  Propagation  by  resting-spores  or  zoogo- 
nidia.  There  are  few  species.  (PL  X,  Fig.  2.) 
Chaetophora. 

Filaments  articulate,  with  primary  branches  radiately  disposed, 
and  secondary  branches  shortly  articulate,  and  attenuated  into 
a  bristle,  the  whole  involved  in  a  gelatinous  mass.  Propaga- 
tion by  zoospores.  (PL  X,  Fig.  3.) 

ORDER  VI.     CHARACE^. 

The  Characeae  are  plants  which  occupy  an  intermediate 
position  between  the  algae  and  the  higher  cryptogams.  Each 
plant  consists  of  an  assemblage  of  long  tubular  cells,  having 
a  distinct  central  axis,  with  whorls  of  branches  projecting  at 
regular  intervals  at  points  called  "nodes."  The  branches  are 
sometimes  spoken  of  as  leaves,  but  they  are  quite  similar  to 
the  stem.  At  the  lower  end  of  the  stem  some  of  the  branches 
(rhizoids)  are  root-like  and  serve  to  give  attachment  and 
stability  to  the  plant.  Reproduction  takes  place  by  a  peculiar 
sexual  process.  Oospheres  or  archegones  form  at  the  base  of 
the  branches  and  are  fertilized  by  peculiar  antherozoids  found 
near  them. 

There  are  two  common  genera, — Nitella  and  Chara.  In 
Nitella  the  stems  and  branches  are  simple  and  naked;  the 
leaves  are  in  whorls  of  5  to  8  and  without  stipules;  the 
leaflets  are  large  and  often  many-celled;  the  sporocarps  arise 
singly  or  in  clusters  in  the  forkings  of  the  leaves,  and  each  has 
a  crown  of  two  superimposed  whorls  of  five  cells  each.  In 
Chara  the  stems  and  lower  branches  are  usually  corticated, 
i.e.  there  is  a  central  tube  surrounded  by  smaller  tubes,  some- 
times spirally  arranged,  forming  a  cortex;  the  leaves  are  in 


220  THE  MICROSCOPY  OF  DRINKING-WATER. 

whorls  of  6  to  12,  and  usually  with  one  or  two  stipules;  the 
leaflets  are  always  one-celled ;  the  sporocarps  arise  from  the 
upper  side  of  the  leaves,  and  each  has  a  crown  of  one  whorl  of 
five  cells.  These  plants  exhibit  beautifully  the  phenomenon 
of  cyclosis,  or  circulation  of  protoplasm.  Some  species  of 
Chara  secrete  calcium  carbonate,  and  from  this  arises  their 
popular  name,  "stone-worts." 


CHAPTER    XIX. 
FUNGI. 

FUNGI  are  flowerless  plants  in  which  the  special  charac- 
teristic is  the  absence  of  chlorophyll  and  starch.  Lacking 
these,  they  are  unable  to  assimilate  inorganic  matter,  and 
consequently  live  a  saprophytic  or  a  parasitic  existence,  that 
is,  they  live  upon  dead  organic  matter  or  in  or  upon  some 
living  host.  They  are  essentially  terrestrial  plants,  but  some 
of  them  live  a  sort  of  semi-aquatic  life. 

Many  very  different  forms  are  included  among  the  Fungi. 
On  the  one  hand  there  are  microscopic  forms, — and  among 
them  some  authors  include  the  bacteria,  because  they  have 
no  chlorophyll, — and  on  the  other  hand  there  are  the  mush- 
rooms, etc.,  which  are  often  of  very  large  size.  Fungi  usually 
consist  of  two  parts,  the  mycelium  and  the  fruit.  The 
mycelium  is  the  vegetative  portion  of  the  plant.  It  is  a  mass 
of  delicate,  jointed,  branched,  colorless  filaments  intertwined 
to  form  a  cottony  or  felty  layer.  It  is  the  spawn  of  mush- 
rooms and  the  common  mold  or  mildew  seen  on  decaying 
vegetable  matter.  The  fruit  consists  of  certain  terminal 
mycelium  filaments  erected  from  the  general  mass  and  bear- 
ing spore-cells  of  various  kinds.  It  is  by  differences  in  the 
method  of  fruiting  or  reproduction  that  the  different  fungi 
are  distinguished  from  each  other. 

The  Fungi,  as  a  class,  are  of  little  importance  in   water 

221 


222  THE   MICROSCOPY   OF  DRINKING-WATER. 

investigation.  They  are  more  often  seen  in  sewage,  and  even 
there  the  number  of  important  genera  is  small.  For  this 
reason  a  general  classification  of  the  Fungi  is  not  given  here, 
but  simply  a  description  of  a  few  common  genera. 

ORDER   SACCHAROMYCETES. 
Saccharomyces. 

Cells  oval  or  somewhat  rounded,  colorless,  with  numerous 
vacuoles.  They  do  not  divide  by  the  ordinary  process  of  cell- 
division,  but  increase  by  a  sort  of  sprouting  or  budding.  A 
knob-like  protuberance  appears  at  one  side  of  the  cell ;  this 
increases  in  size  and  gradually  assumes  the  form  of  the  mother 
cell ;  it  then  separates  and  itself  begins  to  bud,  or  it  remains 
attached,  forming  a  sort  of  irregular  beading  or  branching. 
It  does  not  develop  true  mycelia.  It  also  reproduces  by 
means  of  certain  large  cells  whose  protoplasm  divides  and  forms 
several  spores,  sometimes  called  ascospores.  There  is  no  sexual 
reproduction.  The  Saccharomycetes  are  popularly  called 
yeasts.  They  are  well  known  for  the  alcoholic  fermentation 
which  they  produce  in  sugar.  The  S.  cerevisice  is  the  com- 
mon beer- yeast.  Its  cells  average  about  8  JLI  in  diameter. 
There  are  other  species  which  differ  in  the  shape  and  size  of 
the  cells,  in  the  character  of  the  spores,  in  the  temperature 
and  time  at  which  sprouting  takes  place,  in  the  capacity  to 
ferment  sugars,  in  the  time  required  to  form  yeast-films  in  the 
fermenting  liquid,  etc.  (PL  X,  Fig.  4. ) 

ORDER   ASCOMYCETES. 

Penicillium. 

This  is  the  common  "blue  mold."  The  mycelium  is  com- 
posed of  very  many  colorless,  more  or  less  branched  filaments 
or  hyphae.  The  fertile  hyphae  are  erect  and  septate,  and 
branch  into  a  series  of  compound  branches,  each  of  which 
bears  simple  sterigmata  upon  which  chains  of  oval  conidia  are 
borne.  The  most  common  species  is  P.  glaucum.  It  has  a 
pale  bluish-green  color.  Its  erect  septate  hyphae  are  i  to  2 


FUNGI.  223, 

mm.   long,   bearing  a   minute    brush-like   cluster   of  greenish 
conidia  2-4  /*  in  diameter.      (PI.  X,  Figs.  5  and  6.) 
Aspergillus. 

Mycelium  as  in  Penicillium.  Fertile  hyphae  unseptate, 
swollen  at  apex  (columella),  bearing  simple  flask-shaped 
sterigmata,  with  chains  of  elliptical  or  spherical  conidia. 
Often  small  yellowish  or  reddish  bodies  (perithecia  or  scle- 
rotia)  are  found  upon  the  sterile  hyphae  at  the  base  of  the  fer- 
tile branches.  A.  repens  is  a  common  species.  The  color  is 
light  greenish  or  brownish.  Fertile  hyphae  2-4  mm.  high,  10  j.i 
diam.;  columella  10-30  //,  head  of  conidia  100  JJL,  conidia  5  /*.. 
(PL  X,  Fig.  7.) 

ORDER     PHYCOMYCETES. 

FAMILY  MUCORACEJE. 
riucor. 

Mycelium  saprophytic  or  parasitic,  richly  branched,  forming  a 
felt-like  layer.  The  hyphae  are  seldom  divided  by  septa. 
Conidia  formed  in  sporangia  which  are  spherical  and  borne 
on  erect  hyphae.  A  common  species  is  M.  racemosus.  Its 
sporangia  are  numerous,  20-70  yu  in  diameter,  on  the  ends  of 
long  hyphae.  The  spores  are  smooth,  spherical,  4—8  yu  in  diam- 
eter. Secondary  sporangia  are  sometimes  seen  on  the  main 
fruiting-branch.  The  color  is  whitish,  and  later  a  tawny  brown. 
There  are  many  other  species,  some  of  which  produce  alcoholic 
fermentation  in  sugar.  (PI.  X,  Fig.  8.) 

FAMILY  SAPROLEGNIACK*:. 
Saprolegnia. 

Saprophytic  or  parasitic  on  plants  or  animals  in  water,  some- 
times producing  pathogenic  conditions,  as,  for  example,  in  the 
"salmon-disease."  They  are  often  seen  on  dead  flies,  etc. 
The  mycelium  is  composed  of  colorless  or  grayish  hyphae  of 
large  size  attached  to  the  substratum  by  root-like  processes. 
The  hyphae  are  not  constricted,  as  in  Leptomitus.  Sexual 
reproduction  takes  place  by  means  of  fertilized  oospores. 
Asexual  reproduction  takes  place  by  zoospores  produced  in 
special  club-shaped  zoosporanges  which  are  borne  terminally 


224  THE   MICROSCOPY   OF  DRINKING-WATER. 

upon  certain  hyphae.  The  zoospores  are  numerous,  sometimes 
in  rows ;  they  are  bi-ciliated  and  motile  even  within  the 
zoosporangium.  After  escaping  from  the  zoosporangium  they 
become  covered  with  a  thin  membrane  which  they  throw  off 
before  final  swarming  and  germination.  (PL  XI,  Fig.  i.) 

Achlya. 

Mycelium  similar  to  that  of  Saprolegnia.  The  zoospores  are 
non-motile  when  they  escape  from  the  zoosporangium.  They 
arrange  themselves  in  globular  fashion  outside  the  apex  of  the 
sporangium,  assume  a  thin  membrane,  rest  for  a  time,  and 
ultimately  escape,  swim  about,  and  germinate.  (PI.  XI, 
Fig.  2.) 

Leptomitus. 

Hyphae  long,  cylindrical,  deeply  constricted  at  intervals  and 
at  the  base  of  the  branches.  Near  the  constriction  there  is 
usually  a  globular  body,  like  an  oil-globule.  The  grayish  pro- 
toplasm is  sometimes  arranged  in  concentrated  masses,  and 
sometimes  is  uniformly  distributed.  The  zoospores  are  formed 
in  the  interior  of  club-shaped  terminal  sporangia.  They  resem- 
ble those  of  Saprolegnia.  Leptomitus  is  often  found  in  masses 
in  pipes  conveying  sewage  or  on  the  banks  of  polluted  streams. 
(PL  XI,  Fig.  3.) 


CHAPTER    XX. 
PROTOZOA. 

THE  Protozoa  are  the  lowest  organisms  belonging  to  the 
animal  kingdom.  The  name  Protozoa  was  used  by  the  early 
writers  to  describe  all  minute  organisms,  whether  animal  or 
vegetable,  but  of  late  it  has  come  to  have  a  more  definite 
meaning.  It  is  now  applied  to  those  animal  forms  which  are 
unicellular  or  multicellular  by  aggregation.  Structurally  the 
Protozoa  are  single  cells,  and  where  there  is  an  aggregation 
of  several  cells  each  one  preserves  its  identity.  There  is  no 
differentiation,  no  difference  in  the  function  of  the  different 
cells.  Thus,  the  Protozoa  are  definitely  set  off  from  the 
Metazoa  or  Enterozoa,  which  are  multicellular,  and  which 
have  two  groups  of  cells,  one  group  forming  the  lining  to  a 
digestive  cavity  and  the  other  group  forming  the  body-wall, 
which  differ  both  in  structure  and  in  function.  Most  of  the 
Protozoa  are  strictly  unicellular. 

It  is  extremely  difficult  to  separate  the  unicellular  Protozoa 
from  the  unicellular  Protophyta.  Theoretically  there  is  a 
sharp  distinction  between  the  animal  and  vegetable  kingdoms. 
Definitions  may  be  found  applicable  to  the  higher  types  of 
life,  but  they  overlap  and  become  confused  when  applied  to 
the  lowest  forms.  For  example,  the  fundamental  difference 
betwen  the  two  kingdoms  is  supposed  to  lie  in  the  phenome- 
non of  nutrition.  Plants  can  take  up  the  carbon,  oxygen, 

225 


226  THE   MICROSCOPY   OF  D  R  INKING-  WA 

hydrogen,  and  nitrogen  from  mineral  matter  dissolved  in 
water, — the  nitrogen  in  the  form  of  ammonia  or  nitrates, 
the  carbon  in  the  form  of  carbonic  acid.  Their  food  is  in 
solution;  hence  they  need  no  mouth  or  digestive  apparatus. 
They  absorb  their  nourishment  through  their  entire  surface. 
Animals,  however,  cannot  take  up  nitrogen  in  a  lower  state 
than  is  found  in  the  albumens,  nor  carbon  except  in  combina- 
tion with  oxygen  and  hydrogen  in  the  form  of  fat,  sugar, 
starch,  etc.  The  albumens  and  fats  are  not  soluble  in  water; 
consequently  the  food  of  animals  must  consist  of  more  or  less 
solid  particles.  Animals  therefore  require  a  mouth,  digestive 
cavity,  organs  for  obtaining  their  food,  etc.  As  albumens, 
fats,  etc.,  are  found  in  nature  only  as  products  of  plant  or 
animal  life,  it  follows  that  all  animal  life  is  dependent  upon 
vegetable  or  other  animal  life.  There  are,  however,  certain 
plants  that  live  on  organic  matter  (insectivorous  plants,  pitcher- 
plants)  and  even  have  digestive  cavities,  but  all  their  relations 
show  that  they  are  real  plants.  There  are  other  plants  that 
are  devoid  of  chlorophyll  (Fungi),  yet  no  one  would  think  of 
calling  them  animals.  Then  there  are  many  unicellular  or- 
ganisms that  contain  chlorophyll  and  have  the  vegetable,  or 
holophytic,  mode  of  nutrition,  but  that  resemble  the  animal 
kingdom  in  other  respects.  Such,  for  example,  are  the  Dino- 
flagellata  and  many  of  the  green  Flagellata.  Because  it  is 
difficult  to  draw  a  sharp  line  between  the  vegetable  and 
animal  unicellular  forms  Haeckel  proposed  a  new  group,  the 
Protista,  lying  between  the  two  kingdoms.  This  group  has 
been  since  known  as  the  Phytozoa.  The  term  is  not  used  in 
this  work,  but  the  organisms  have  been  placed  in  the  one  or 
the  other  of  the  two  kingdoms  according  to  the  best  available 
authority. 

The  Protozoan  Cell. — The  protozoan  cell,  or  the  indi- 


PROTOZOA  227 

vidual  protozoan,  is  a  single  mass  of  sarcode,  or  protoplasm, 
that  possesses  in  a  general  way  all  the  properties  of  the  proto- 
plasm of  higher  animal  cells.  It  has  a  certain  amount  of 
irritability  and  movement,  it  assimilates  food,  it  grows,  and 
reproduces  its  kind.  It  is  subject  to  the  same  chemical  and 
physical  reactions  that  are  observed  in  higher  forms.  In 
size  it  varies  from  the  tiniest  corpuscle  to  a  mass  an  inch  in 
diameter.  It  is  irregular  in  form,  without  a  definite  bound- 
ary; or  it  has  a  cell-wall  and  a  definite  symmetrical  outline. 
Internally  the  cell  usually  contains  a  solid  nucleus  or  a  nuclear 
substance  distributed  through  the  cell  and  recognized  by 
staining.  It  usually  contains  a  contractile  vacuole,  which 
may  be  seen  to  expand  and  contract,  discharging  a  watery  or 
gaseous  matter  through  the  cell.  There  are  also  permanent 
vacuoles  of  watery  fluid,  gastric  vacuoles  formed  by  the 
water  taken  in  with  the  food,  oil-globules,  and  solid  particles 
of  starch,  chlorophyll,  etc.  Externally  there  may  be  a  cor- 
tical substance, — a  denser  layer  of  protoplasm  giving  definite 
shape  to  the  cell — that  is  sometimes  contractile.  The  ex- 
terior protoplasm  may  contain  such  secreted  products  as 
chitin,  a  nitrogenous  horny  matter,  or  cellulose,  a  non- 
nitrogenous  substance,  forming  a  cell-wall,  cell-cuticle,  or 
matrix.  Substances  may  be  deposited  even  outside  of  the 
protoplasmic  layer.  If  perforated  they  are  known  as  shells; 
if  closed  entirely,  as  cysts.  Cysts  are  usually  of  a  horny 
nature  and  are  temporary  products.  External  secretions  of 
calcium  carbonate,  silicates,  etc.,  are  sometimes  present. 

The  cell-protoplasm  often  exhibits  certain  internal  flowing 
movements,  described  as  the  "streaming  of  the  protoplasm." 
Portions  of  the  protoplasm  often  extend  outwards,  forming 
processes.  These  are  of  two  kinds,  and  the  distinction  be- 
tween them  has  been  used  as  a  basis  of  classification.  Those 


228  THE   MICROSCOPY   OF  DRINKING-WATER. 

protozoa  that  have  lobose,  filamentous  processes,  known  as 
pseudopodia,  are  called  Myxopods;  those  that  have  motile 
hair-like  processes,  known  as  cilia  or  flagella,  are  called 
Mastigopods. 

The  simplest  Protozoa  absorb  solid  particles  of  food  at  any 
point  on  their  surface.  Digestion  takes  place  within  the  cell. 
Protozoa  higher  in  the  scale  of  life  have  a  distinct  oral  aper- 
ture through  which  the  food  enters,  a  sort  of  pharyngeal 
passage,  and  an  anal  aperture  through  which  undigested  por- 
tions of  food  are  expelled.  There  is  no  real  digestive  cavity. 
Some  Protozoa  exhibit  a  simple  kind  of  respiration.  Experi- 
ment has  shown  that  they  take  up  oxygen  and  give  out 
carbonic  acid.  Multiplication  takes  place  by  binary  division, 
by  encystment  and  spore-formation,  by  conjugation  followed 
by  spore-formation,  or  by  conjugation  followed  by  increased 
power  of  division.  Strictly  there  is  no  sexual  reproduction, 
though  in  certain  instances  there  are  processes  corresponding 
to  it. 

Various  classifications  have  been  suggested  for  the  Pro- 
tozoa. None  are  entirely  satisfactory.  Butschli  has  divided 
the  Protozoa  into  four  classes:  the  Sarcoda,  Sporozoa,  Masti- 
gophora,  and  Infusoria.  So  far  as  fresh-water  forms  are  con- 
cerned, the  Sarcoda  represent  the  Rhizopoda  as  described  by 
Leidy.  The  Mastigophora  and  Infusoria  are  both  included 
by  the  word  Infusoria  as  used  by  Kent.  Btitschli's  classifica- 
tion with  some  modifications  is  given  below,  so  far  as  it  relates 
to  the  forms  with  which  the  water  analyst  is  concerned. 
Many  families  and  some  entire  orders  are  omitted. 

CLASS   RHIZOPODA. 

Protozoa  provided  with  variable,  retractile  root-like  proc- 
esses or  pseudopodia;  naked  or  enclosed  in  a  carapace  or 


PROTOZOA.  229 

external  skeleton  that  is  chitinous,  calcareous,  or  siliceous; 
generally  one  and  sometimes  more  than  one  nucleus;  contract- 
ile vacuole  present  or  absent. 

There  are  five  sub-classes — -Lobosa,  Reticularia,  Heliozoa, 
Radiolaria,  and  Labyrinthulidea.  The  two  latter  are  marine 
forms  and  therefore  are  omitted.  The  Lobosa  and  Reticularia 
are  creeping  animals;  the  Heliozoa  are  swimmers. 

SUB-CLASS  LOBOSA. 

Rhizopoda  in  which  the  "amoeba- phase"  predominates  in 
permanence  and  physiological  importance.  Pseudopodia 
lobose,  not  filamentous,  arborescent,  or  reticulate.  A  denser 
external  layer  of  protoplasm  usually  noticed.  Provided  with 
one  or  more  nuclei  and  usually  with  a  contractile  vacuole. 
Reproduction  commonly  effected  by  simple  fission,  sometimes 
by  a  kind  of  budding. 

Amoeba. 

A  soft,  colorless,  granular  mass  of  protoplasm ;  possessing 
extensile  and  contractile  power;  devoid  of  investing  mem- 
brane, but  having  an  external  thickening  of  protoplasm ;  with 
variable,  lobose,  finger-like  processes ;  ingesting  food  by  flow- 
ing around  and  engulfing  it ;  the  absorbed  food-material 
(diatoms,  algae,  etc.)  is  often  conspicuous.  There  are  several 
species  that  vary  m  size  and  in  the  character  of  the  pseudo- 
podia.  A  common  habitat  is  the  superficial  ooze  of  ponds  or 
ditches.  (PI.  XI,  Fig.  4.) 
Arcella. 

An  amoeba-like  organism  enclosed  in  a  chitinoid  shell  that  is 
variable  in  shape,  but  more  or  less  campanulate  or  dome- 
shaped,  and  that  has  a  circular,  somewhat  concave  base. 
When  seen  from  above,  it  is  disc -shaped,  with  a  pale  circular 
spot  in  the  middle ;  when  seen  from  the  side,  the  upper  sur- 
face is  strongly  convex.  The  shell  usually  has  a  brown  color, 
and  is  sometimes  smooth  and  sometimes  hexagonally  marked. 


230  THE   MICROSCOPY   OF  DRINKING-WATER. 

The  protoplasmic  mass  occupies  the  central  portion  of  the  shell, 
but  pseudopodia  project  through  an  opening  in  the  concave 
base.  There  are  many  species,  differing  in  shape  and  in  the 
marks,  ridges,  etc.,  on  the  shell.  A.  vulgaris  is  the  most 
common.  (PI.  XI,  Figs.  5  and  6.) 
Difflugia. 

Body  enclosed  in  a  spherical  or  pear-shaped  membrane  in 
which  sand-grains,  etc.,  are  embedded.  The  lower  part  is 
sometimes  prolonged  as  a  neck,  at  the  end  of  which  is  situated 
the  mouth,  through  which  finger-like  pseudopodia  may  project. 
The  surface  of  the  shell  is  very  rough  and  usually  has  a 
brownish  or  a  gray  color.  Diatoms,  etc.,  are  frequently 
attached  to  the  shell.  The  contained  protoplasmic  mass 
frequently  has  a  green  color,  but  the  pseudopodia  are  colorless. 
There  are  several  species,  varying  in  shape  and  size.  The 
diameter  of  DifHugia  shells  varies  from  35  to  300  /i.  (PL  XI, 
Fig.  7-) 

SUB-CLASS  RETICULARIA. 

Rhizopoda  covered  with  a  secreted  shell-like  membrane 
with  agglutinated  particles  of  lime  or  sand.  The  projected 
pseudopodia  are  not  finger-like,  as  in  the  Lobosa,  but  thread- 
like and  delicately  and  acutely  branched.  The  external 
denser  layer  of  protoplasm  is  not  as  well  marked  as  in  the 
Lobosa.  The  shell  is  sometimes  perforated  by  apertures. 

Euglypha. 

Body  enclosed  in  a  hyaline,  ovoid  shell,  composed  of  regular 
hexagonal  plates  of  chitinoid  membrane,  arranged  in  alternat- 
ing longitudinal  series.  At  the  mouth  the  plates  form  a  serrated 
margin.  The  upper  portion  of  the  shell  is  sometimes  provided 
with  spines.  The  protoplasm  is  almost  entirely  enclosed  by 
the  shell ;  the  pseudopodia  are  delicate  and  branched.  There 
are  several  species.  (PI.  IX,  Fig.  8.) 
Prinema. 

Body  enclosed  in  a  hyaline,  pouch-like  shell,  with  long  axis  in- 
clined or  oblique,  and  with  mouth  subterminal.  Dome 


PROTOZOA.  231 

rounded  ;  mouth  inverted,  circular,  beaded  at  border.  Pseudo- 
podia  as  in  Euglypha,  but  fewer  in  number.  The  two  genera 
are  quite  similar,  but  Trinema  is  usually  much  smaller.  One 
species.  (PI.  XI,  Fig.  9.) 


SUB-CLASS  HELIOZOA. 

Rhizopoda  generally  spherical  in  form,  with  numerous 
radial,  filamentous  pseudopodia,  which  ordinarily  exhibit  little 
change  of  form,  though  they  are  elastic  and  contractile. 
Protoplasm  richly  vacuolated.  One  or  more  nuclei  and  con- 
tractile vacuoles.  Chlorophyll  grains  sometimes  present. 
Skeleton  products  sometimes  present.  The  Heliozoa  are 
generally  found  in  fresh  water.  They  are  closely  related  to 
the  marine  Radiolaria. 

Actinophrys. 

A  spherical  mass  of  colorless  protoplasm  seemingly  filled  with 
small  bubbles,  with  numerous  long,  fine  rays  springing  from  all 
parts  of  the  surface.  Contractile  vesicle  large  and  active. 
The  organism  moves  with  a  slow  gliding  motion.  It  feeds  on 
smaller  protozoa,  algae-spores,  etc.  The  most  important  species 
is  A.  sol,  otherwise  known  as  the  "sun-animalcule."  It  is 
very  common  in  swamp-water.  (PI.  XI,  Fig.  10.) 
Heterophrys. 

Like  Actinophrys  in  general  form,  but  with  the  body  enveloped 
with  a  thick  stratum  of  protoplasm  defined  by  a  granulated  or 
thickly  villous  surface  and  penetrated  by  the  pseudopodal  rays. 

CLASS  MASTIGOPHORA. 

Protozoa  bearing  one  or  more  lash-like  flagella,  occa- 
sionally supplemented  by  cilia,  pseudopodia,  etc.  With  an 
indistinct,  diffuse,  or  definite  ingestive  system,  and  usually 
with  one  or  more  contractile  vesicles.  Multiplication  takes 
place  by  fission  and  by  sporulation  of  the  entire  body-mass, 


232  7 'HE   MICROSCOPY   OF  DRINKING-WATER. 

the  process  often  being  preceded  by  conjugation  of  two  or 
more  zooids.  The  term  Flagellata  is  used  by  some  writers  to 
describe  this  class  of  Protozoa. 


SUB-CLASS  FLAGELLATA. 

Nucleated  cells,  with  a  definite,  corticate,  external  layer  of 
protoplasm  and  provided  with  one  or  more  vibratile  flagella. 
Food  commonly  ingested  through  an  oral  aperture  in  the 
cortical  protoplasm,  though  some  genera  contain  chlorophyll 
and  are  sustained  by  nutritional  processes  resembling  those  of 
plants.  In  some  genera  the  cuticle  is  developed  into  stalks 
or  collar-like  outgrowths.  Others  produce  chitinous  shells  or 
masses  of  jelly  and  are  connected  into  arborescent  or  spherical 
colonies.  Food-particles,  starch-gains,  chromatophore  and 
chlorophyll  corpuscles,  oil-globules,  pigment-spots  (eye-spots) 
are  often  observed  in  the  protoplasm  of  the  cell. 

The  flagella  of  the  Flagellata  offer  an  interesting  study. 
They  are  essentially  different  from  cilia  in  their  movement. 
Cilia  are  simply  alternately  bent  and  straightened.  Flagella 
exhibit  lashing  movements  to  and  fro  and  also  throw  them- 
selves into  serpentine  waves.  There  are  two  kinds  of  flagella, 
distinguished  by  their  movement — pulsella  and  tractella. 
The  former  serve  to  drive  the  organism  forward  in  the  manner 
of  a  tadpole's  tail.  These  are  never  found  on  the  Flagellata. 
The  tractellum  is  carried  in  front  of  the  body  and  draws  the 
organism  after  it,  as  a  man  uses  his  arms  in  swimming. 
The  flagella  of  the  Flagellata  are  always  tractella. 


PROTOZOA.  233 

ORDER  MONADINA. 

Small,  simple  Flagellata,  often  naked  or  amoeboid,  usually 
colorless,  seldom  with  chromatophores.  With  a  single,  large, 
anterior  flagellum  or  sometimes  with  two  additional  flagella. 
Mouth  area  often  wanting,  never  produced  into  a  well-devel- 
oped pharynx. 

FAMILY  CERCOMONADINA. 
Cercomonas. 

Animalcules  free-swimming,  ovate  or  elongate,  plastic,  with  a 
single  long  flagellum  at  anterior  extremity  and  a  caudal  fila- 
ment at  the  opposite  extremity  ;  no  oral  aperture.  There  are 
several  species.  Their  length  varies  from  10  to  25  fit.  (PI. 
XII,  Fig.  i.) 

FAMILY  HETEROMONADINA. 

Monas. 

Very  minute,  free-swimming  animalcules,  colorless,  globose 
or  ovate,  plastic,  with  no  distinct  cuticle ;  flagellum  single, 
terminal ;  no  distinct  mouth.  Several  species,  commonly 
found  in  vegetable  infusions.  Their  length  varies  from  2 
to  10  JA.  They  move  with  a  "swarming"  motion.  (PI.  XII, 
Fig.  2.) 

Anthophysa. 

Animalcules  colorless,  obliquely  pyriform,  attached  in  spher- 
ical clusters  to  the  extremities  of  slightly  flexible,  granular, 
opaque,  more  or  less  branching  pedicles ;  two  flagella,  one 
longer  than  the  other ;  no  distinct  mouth.  In  the  common 
species,  A.  vegetans,  the  pedicle  is  dark  brown  and  longi- 
tudinally striated.  The  detached  stems  somewhat  resemble 
Crenothrix  when  observed  with  a  low  power.  Zooids  about 
5  fit  long;  clusters  25  fit  in  diameter.  Common  in  swamp- 
water.  (PI.  XII,  Fig.  3.) 

ORDER  EUGLENOIDEA. 

Somewhat    large    and    highly    developed     monoflagellate 
forms,  with  firm,  contractile,  elastic  cortical  substance;  some 


234  THE    MICROSCOPY   OF  DRINKING-WATER. 

forms  are  stiff,  others  are  capable  of  annular  contraction  and 
worm-like  elongation.  At  the  base  of  the  flagellum  there  is 
a  mouth  leading  into  a  pharyngeal  tube,  near  which  is  a  con- 
tractile vacuole.  Rarely  with  two  flagella. 

FAMILY  CCELOMONADINA. 
Ccelomonas. 

Animalcules  free-swimming,  monoflagellate,  highly  contractile 
and  variable  in  form,  with  distinct  oral  aperture  and  a  spher- 
oidal pharyngeal  chamber;  nucleus  and  contractile  vacuole 
conspicuous ;  no  trichocysts ;  with  innumerable  green  chloro- 
phyll granules.  Nutrition  largely  vegetal.  One  species. 
Length  about  50  jj.  (PI.  XII,  Fig.  4.) 
Raphidomonas  (Gonyostomum). 

Animalcules  free-swimming ;  ovate-elongate,  flexible  body, 
widest  anteriorly  and  tapering  posteriorly,  two  to  three  times 
as  long  as  wide ;  two  flagella,  one  of  them  trailing ;  oral 
aperture  at  anterior  end  conducts  to  a  conspicuous  triangular  or 
Innate  pharyngeal  chamber  ;  contractile  vacuole  conspicuous  ; 
nucleus  ovate  ;  a  brownish  germ -sphere  posteriorly  located  ; 
many  large  bright  green  chlorophyll  bodies  ;  numerous  rod- 
like  bodies  called  trichocysts ;  oil-globules  often  present. 
Length  40  to  70  //.  Reproduction  by  spores  formed  in  the 
germ-sphere.  One  species,  R.  semen.  The  genus  Trentonia, 
described  by  Dr.  A.  C.  Stokes,  is  similar  to  Raphidomonas 
except  that  it  has  no  trichocysts.  (PL  XII,  Fig.  5.) 

FAMILY  EUGLENINA. 
Euglena. 

Free-swimming  animalcules,  fusiform  or  elongate,  exceedingly 
flexible  in  form ;  with  highly  elastic  cuticle  terminating  pos- 
teriorly in  a  tail-like  prolongation ;  endoplasm  bright  green 
or  reddish ;  flagellum  flexible,  issuing  from  an  anterior  notch 
at  the  bottom  of  which  is  the  oral  aperture  and  a  red  pigment - 
spot.  There  are  several  common  species.  E.  viridis  is  the 
most  common.  It  is  often  found  in  immense  numbers  in 
stagnant  pools,  forming  a  characteristic  green  or  reddish  scum. 
Length  varies  from  40  to  150  //.  E.  acus  is  an  elongated  form 


PROTOZOA.  235 

with  tapering  ends.  It  is  longer  than  E.  viridis,  but  less  broad. 
It  is  also  less  variable  in  form.  E.  deses  is  a  very  long  cylin- 
drical form.  (PI.  XII,  Fig.  6.) 

Trachelomonas. 

Monoflagellate  animalcules,  changeable  in  form,  enclosed 
within  a  free-floating,  spheroidal,  indurated  sheath  or  lorica  ; 
flagellum  protruded  through  an  aperture  in  the  lorica.  The 
color  of  the  animalcule  is  green,  with  a  red  pigment-spot ; 
the  color  of  the  lorica  is  generally  a  reddish  brown.  There 
are  several  species.  Diameter  of  lorica  generally  about  25  /*. 
(PL  XII,  Fig.  7.) 

Phacus. 

Free-swimming  animalcules;  form  persistent,  leaf-like,  with 
sharp-pointed,  tail-like  prolongation ;  terminal  oral  aperture 
and  tubular  pharynx ;  flagellum  long,  vibratile ;  surface  in- 
durated ;  endoplasm  green,  with  red  pigment-spot ;  contractile 
vacuole  large,  subspherical.  Length  about  50  //,  but  quite 
variable.  (PL  XII,  Fig.  8.) 

ORDER  ISOMASTIGODA. 

Small  and  middle-sized  forms  of  monaxonic,  rarely  bilat- 
eral shape.  Fore  end  with  two  or  more  flagella.  Some  are 
colored,  some  colorless;  naked  or  with  strong  cuticle  or 
secreting  an  envelope.  Nutrition  generally  holophytic  (i.e. 
likg  a  green  plant). 

FAMILY  CHRYSOMONADINA. 
Synura. 

Free-swimming  animalcules,  united  in  subspherical  social  clus- 
ters, each  zooid  contained  in  a  separate  membranous  sheath  or 
lorica,  the  posterior  extremities  of  which  are  stalk-like  and  con- 
fluent; two  subequal  flagella,  sometimes  long;  pigment-spots 
minute  or  absent ;  two  brown  color-bands  produced  equally 
throughout  the  length  of  the  two  lateral  borders ;  a  vacuolar 
space  at  the  anterior  extremity  and  several  contractile  vacuoles  ; 
oil -globules  often  observed.  Length  of  individual  zooids  about 
35  /* ;  diameter  of  clusters  varies  from  30  to  100  /A.  There  is 


236  THE   MICROSCOPY   OF  DRINKING-WATER. 

one  species,  £.  uvella,  with  several  varieties.  The  colonies  move 
with  a  brisk  rolling  motion,  caused  by  the  combined  action  of 
the  flagella.  Common  in  swamp-waters.  (PL  XII,  Fig.  9.) 

Uvella. 

An  uncertain  genus.  Uvella  differs  from  Synura  in  the  non- 
possession  of  a  separate  investing  membrane  or  lorica  and  by 
the  posterior  location  of  the  contractile  vacuole.  There  are 
usually  few  zooids  in  the  cluster.  (PL  XII,  Fig.  10.) 

Syncrypta. 

Free-swimming  animalcules,  united  into  spherical  clusters  as  in 
Synura,  without  lorica,  but  with  the  entire  colony  immersed 
within  a  gelatinous  matrix,  beyond  the  periphery  of  which  the 
flagella  alone  project ;  two  subequal  flagella ;  brownish  lateral 
color-bands  evenly  developed ;  one  or  two  pigment-spots ; 
contractile  vacuole  between  the  color-bands.  Length  of 
zooids  about  10  yw.  Diameter  of  colony  about  50  /u,  including 
gelatinous  zooglcea.  There  is  but  one  species,  £.  volvox.  It 
resembles  Synura.  It  is  not  common.  PL  XII,  Fig.  u.) 

Uroglena. 

Animalcules  forming  almost  colorless  spheroidal  colonies  barely 
visible  to  the  naked  eye.  The  matrix  of  the  colony  is  a  trans- 
parent gelatinous  shell  filled  with  a  watery  substance.  The 
zooids  are  embedded  on  the  periphery,  with  their  flagella 
extending  outwards  and  by  their  vibration  causing  the  colony 
to  revolve.  The  zooids  are  pyriform,  with  anterior  border 
rounded  and  truncated,  tapering  posteriorly  and  sometimes 
continued  backwards  as  a  contractile  thread  ;  with  two  light 
yellowish-green  pigment-bands ;  one  eye-spot  at  the  base  of 
the  flagella  ;  two  unequal  flagella ;  one  or  more  contractile 
vacuoles ;  oil-globules  and  a  large  amylaceous  body  often 
present.  Length  of  zooids  is  about  6  to  12  /,/.  The  colonies 
are  from  200  to  500  ^  in  diameter.  There  are  several  rather 
indistinct  species.  The  zooids  multiply  by  division  into  twos 
or  fours.  The  colonies  also  divide,  a  hollow  first  appearing  on 
one  side,  followed  by  a  rounding  at  the  two  poles  and  a  sub- 
sequent twisting  apart.  The  Uroglena  colonies  are  very  fra- 
gile. (PL  XII,  Figs.  12  and  13.) 


PROTOZOA.  237 

Oinobryon. 

Animalcules  with  urn-  or  trumpet -shaped  loricae  attenuated  pos- 
teriorly and  set  one  into  another  so  as  to  form  a  compound 
branching  polythecium.  The  zooids  are  elongate-ovate,  at- 
tached to  the  bottom  of  the  loricae  by  transparent  elastic 
threads  ;  two  unequal  flagella  ;  two  brownish  or  greenish  lateral 
color-bands  ;  a  conspicuous  pigment-spot ;  nucleus  and  con- 
tractile vacuole  sub-central.  The  polythecium  is  constructed 
through  the  successive  terminal  gemmation  of  the  zooids. 
Length  of  separate  loricae  1 5  to  60  ju.  The  polythecium  may 
contain  from  2  to  500  loricae.  The  usual  number  is  bet.veen 
25  and  50.  Reproduction  takes  place  by  spore-formation. 
The  spores  sometimes  remain  attached  to  the  polythecium,  or 
they  may  become  scattered.  When  free  they  are  liable  to  be 
mistaken  for  small  Cyclotella.  The  spores  are  from  8  to  20  /* 
in  diameter.  There  are  several  species.  D.  sertularia  is  the 
most  common.  (PI.  XIII,  Fig.  i.) 

Cryptomonas. 

Free-swimming  animalcules,  illoricate,  but  persistent  in  form, 
ovate  or  elongate,  compressed  asymmetrically ;  flagella  two, 
long,  equal  in  length,  issuing  from  a  deep  groove  or  furrow ; 
large  oral  aperture  at  the  base  of  the  flagella  continued  back- 
wards as  a  tubular  pharynx ;  two  lateral  bright  green  color- 
bands  ;  conspicuous  nucleus  and  contractile  vacuole ;  oil- 
globules  often  present.  Length  from  40  to  60  yu.  (PI.  XIII, 
Fig.  2.) 

Mallomonas. 

Free-swimming  animalcules,  oval  or  elliptical,  persistent  in 
shape;  surface  covered  with  overlapping  horny  plates  from 
which  arise  long  hair-like  setae  ;  under  low  power  the  surface 
has  a  crenulated  appearance.  One  long,  slender  anterior 
flagellum  ;  indistinct  contractile  vacuole.  Endoplasm  vacuolar, 
greenish  or  yellowish.  Length  from  20  to  40  //.  (PI.  XIII, 
Fig.  30 
FAMILY  CHLAMYDOMONADINA. — This  family  is  often  referred  to 

the  vegetable  kingdom. 

Chlamydomonas. 

Animalcules  ovate,  with  two  or  more  flagella,  one  large  green 


23$  THE   MICROSCOPY  OF  DRINKING-WATER. 

color-mass,  a  delicate  membranous  shell,  usually  with  a  pig- 
ment-spot and  one  or  more  contractile  vacuoles.  The  proto- 
plasm divides  into  new  individuals  within  the  envelope. 
Length  from  10  to  30  /*.  (PI.  XIII,  Fig.  4.) 

FAMILY  VOLVOCINA.  —  Often   included  under  Protozoa.     See  page 


SUB-CLASS  CHOANOFLAGELLATA. 

Mastigophora  provided  with  an  upstanding  collar  sur- 
rounding the  anterior  pole  of  the  cell,  from  which  the  single 
flagellum  springs.  (Omitted  from  this  work.) 


SUB-CLASS  DINOFLAGELLATA. 

Mastigophora  are  characterized  by  the  presence  of  a 
longitudinal  groove,  marking  the  anterior  region  and  the 
ventral  surface,  and  from  which  a  long  flagellum  projects. 
In  every  genus  but  one  there  is  also  a  transverse  groove  in 
which  lies  horizontally  a  second  flagellum,  at  one  time  mis- 
taken for  a  girdle  of  cilia.  The  animalcules  are  bilaterally 
asymmetrical.  They  are  occasionally  naked,  but  most  genera 
are  covered  with  a  cuticular  shell  of  cellulose,  either  entire 
or  built  of  plates.  The  endoplasm  contains  chlorophyll, 
starch-granules,  and  a  brown  coloring  matter  similar  to  that 
of  diatoms.  The  nucleus  is  large  and  branching.  There  is 
no  contractile  vacuole.  Multiplication  takes  place  by  trans- 
verse binary  fission. 

Because  of  the  presence  of  the  cellulose  shell,  chlorophyll, 
starch-granules,  and  a  holophytic  (vegetal)  mode  of  nutrition 
the  Dinoflagellata  are  often  classed  in  the  vegetable  kingdom. 
Many  of  the  Dinoflagellata  are  marine  forms.  Some  are 
phosphorescent. 


PROTOZOA.  239 

Peridinium. 

Free-swimming  animalcules  enclosed  within  a  cellulose  shell 
composed  of  polygonal  facets.  With  a  high  power  the  facets 
exhibit  a  delicate  reticulation.  A  transverse  groove  divides 
the  body  into  two  subequal  parts.  A  second  groove  extends 
from  the  first  towards  the  apical  extremity.  Two  flagella,  one 
in  the  transverse  groove,  the  other  proceeding  from  the  junc- 
tion of  the  two  grooves.  Color  yellowish  green  or  brown. 
There  are  one  or  more  pigment-spots.  Length  from  40  to 
75  yu.  There  are  several  species.  P.  tabulatum  is  the  most 
common.  (PI.  XIII,  Fig.  5.) 

Ceratium. 

Free-swimming  animalcules  enclosed  within  a  shell  consisting 
of  two  subequal  segments,  one  or  both  of  which  are  produced 
into  conspicuous  horn-like  prolongations,  often  covered  with 
tooth-like  processes.  There  is  a  central  transverse  furrow  and 
a  second  groove  extending  from  the  centre  of  the  ventral  aspect 
towards  the  anterior  pole.  Two  flagella,  one  of  which  lies  in 
the  transverse  groove.  The  brown  color  is  not  as  marked  as 
in  Peridinium.  Length  from  25  to  150  >u.  There  are  several 
species,  varying  considerably  in  the  character  of  the  horn-like 
projections.  (PI.  XIII,  Fig.  6.) 

Glenodinium 

Free-swimming  animalcules  covered  with  a  smooth,  cellulose 
shell  not  made  up  of  facets,  consisting  of  two  subequal  parts. 
There  is  a  conspicuous  transverse  groove  and  a  much  less  con- 
spicuous secondary  groove.  Two  typical  flagella.  Body 
ovate.  Color  brownish.  Pigment-spot  sometimes  present. 
Length  about  40  to  55  yw.  Glenodinium  is  often  surrounded 
by  a  wide,  irregular  mass  of  jelly.  (PI.  XIII,  Fig.  7.) 

Gymnodinium. 

Quite  similar  to  Peridinium,  but  without  a  protecting  shell. 

SUB-CLASS  CYSTOFLAGELLATA. 
Marine  forms. 


240  THE   MICROSCOPY   OF  DRINKING-WATER. 

CLASS  INFUSORIA. 

In  its  broadest  sense  the  word  Infusoria  includes  all  the 
Protozoa  except  the  Rhizopoda  and  Sporozoa.  As  used 
here,  following  Biitschli,  it  includes  only  the  Ciliata  and 
Suctoria. 

SUB-CLASS  CILIATA. 

Protozoa  of  relatively  large  size,  furnished  with  cilia,  but 
not  with  flagella.  The  cilia  occur  as  a  single  band  surround- 
ing the  oral  aperture  or  are  dispersed  over  the  entire  body. 
Modification  of  the  cilia  into  setae  or  styles  is  sometimes 
observed.  There  is  generally  a  well-developed  oral  and  anal 
aperture.  The  nucleus  varies  in  different  genera.  Besides 
one  larger,  oblong  nucleus  a  smaller  one  (paranucleus)  is  often 
present.  One  or  more  contractile  vacuoles  present.  They 
all  possess  a  delicate  but  well-defined  ectoderm,  elastic,  but 
constant  in  form.  They  occur  naked  or  enclosed  in  horny  or 
siliceous  shells  or  in  gelatinous  envelopes.  Some  genera  are 
stalked.  Multiplication  takes  place  by  transverse  fission. 
Conjugation  has  been  observed,  but  the  part  that  it  plays  in 
the  life-history  is  not  well  known.  Many  of  the  Ciliata  are 
parasites  in  higher  animals. 

The  Ciliata  are  divided  into  four  orders  according  to  the 
character  and  distribution  of  their  cilia. 

ORDER  HYPOTRICHA. 

Ciliata  in  which  the  body  is  flattened  and  the  locomotive 
cilia  are  confined  to  the  ventral  surface,  and  are  often  modified 
and  enlarged  to  the  condition  of  muscular  appendages. 
Usually  an  adoral  band  of  cilia,  like  that  of  Heterotricha. 
Dorsal  surface  smooth  or  provided  with  tactile  hairs  only. 
Mouth  and  anus  conspicuous. 


PROTOZOA.  241 

Euplotes. 

Animalcules  free-swimming,  encuirassed,  elliptical  or  orbicular, 
with  sharp  laminate  marginal  edges,  and  usually  a  plane  ven- 
tral, and  convex,  sometimes  furrowed,  dorsal  surface.  Peri- 
stome-field  arcuate,  extending  backwards  from  the  frontal  border 
to  or  beyond  the  centre  of  the  ventral  surface,  sometimes  with 
a  reflected  and  ciliate  inner  border.  Frontal  styles  six  or  seven 
in  number  ;  three  or  more  irregularly  scattered  ventral  styles, 
and  five  anal  styles  ;  four  isolated  caudal  styles  along  the 
posterior  margin.  Endoplast  linear.  Single  spherical  con- 
tractile vesicle  near  anal  aperture.  Length  about  125  yw. 
(PL  XIII,  Fig.  8.) 

ORDER  PERITRICHA. 

Ciliata  with  the  cilia  arranged  in  one  anterior  circlet  or  in 
two,  an  anterior  and  a  posterior;  the  general  surface  of  the 
body  destitute  of  cilia.  The  Peritricha  are  sometimes  divided 
into  two  suborders,  the  free-swimming  forms  and  the  attached 
forms. 

Halteria. 

Animalcules  free-swimming,  colorless,  more  or  less  globose, 
terminating  posteriorly  in  a  rounded  point.  Oral  aperture 
terminal,  eccentric,  associated  with  a  spiral  or  subcircular 
wreath  of  large  cirrose  cilia.  A  zone  of  long  hair-like  setae 
or  springing-hairs  developed  around  the  equatorial  region, 
the  sudden  flexure  of  which  appendages  enables  the  organism 
to  progress  through  the  water  by  a  series  of  leaping  movements, 
in  addition  to  their  ordinary  swimming  motions.  Length  15 
to  30  yu.  There  are  several  species,  some  of  them  colored 
green.  (PL  XIII,  Fig.  9.) 
Vorticella. 

Animalcules  ovate,  spheroidal,  or  campanulate,  attached  pos- 
teriorly by  a  simple  undivided,  elongate  and  contractile, 
thread-like  pedicle  ;  the  pedicle  enclosing  an  elastic,  spirally 
disposed,  muscular  fibrilla,  and  assuming  suddenly  on  con- 
traction a  much-shortened  and  usually  corkscrew-like  contour. 


242  THE   MICROSCOPY   OF  DRINKING-WATER. 

Adoral  system  consisting  of  a  spirally  convolute  ciliary  wreath, 
the  right  limb  of  which  descends,  into  the  oral  cleft,  the  left 
one  obliquely  elevated  and  encircling  the  ciliary  disk.  The 
entire  adoral  wreath  contained  within  and  bounded  by  a  more 
or  less,  distinctly  raised  border — the  peristome — between  which 
and  the  elevated  ciliary  disk,  on  the  ventral  side,  the  widely 
excavated  cleft  or  vestibulum  is  situated.  The  vestibulum  is 
continued  further  into  a  conspicuous  cleft-like  pharynx,  and 
terminates  in  a  narrow  tubular  oesophagus.  Anal  aperture 
opening  into  the  vestibulum.  Contractile  vesicle  single, 
spherical,  near  the  vestibulum.  Nucleus  elongate.  Multipli- 
cation by  longitudinal  fission,  by  gemmation,  and  by  the 
development  of  germs.  There  exists  a  very  large  number  of 
species,  varying  considerably  in  size  and  shape.  The  length 
varies  from  25  to  200  p.  Vorticella  are  often  found  floating 
in  water  attached  to  masses  of  Anabsena,  etc.  (PI.  XIII,. 
Fig.  10.) 

Zoothamnium. 

Animalcules  structurally  identical  with  those  of  Vorticella, 
ovate,  pyriform,  or  globular,  often  dissimilar  in  shape  and 
of  two  sizes,  stationed  at  the  extremities  of  a  branching,  highly 
contractile  pedicle  or  zoodendrium.  Numerous  species. 

Epistylis. 

Animalcules  campanulate,  ovate,  or  pyriform,  structurally  sim- 
ilar to  Vorticella,  attached  in  numbers  to  a  rigid,  uncon- 
tractile,  branching,  tree-like  pedicle  or  zoodendrium ;  the 
zooids  usually  of  similar  size  and  shape.  Numerous  species. 
(PI.  XIII,  Fig.  n.) 

ORDER  HETEROTRICHA. 

Ciliata  possessing  two  distinct  systems  of  cilia,  one  a  band 
or  spiral  or  circlet  of  long  cilia  developed  in  the  oral  region, 
the  other  composed  of  short,  fine  cilia  covering  the  entire 
body.  The  cortical  layer  is  usually  highly  differentiated. 

Tintinnus. 

Animalcules   ovate    or   pyriform,    attached    posteriorly   by   a 


PROTOZOA.  243 

slender  retractile  pedicle  within  an  indurated  sheath  or  lorica. 
The  shape  of  the  lorica  is  generally  cylindrical  ;  it  is  free- 
floating  ;  it  is  somewhat  mucilaginous  and  attracts  to  its  outer 
surface  foreign  particles,  such  as  grains  of  inorganic  matter, 
diatom-shells,  etc.  The  peristome-field  of  the  organism  occu- 
pies the  entire  anterior  border,  circumscribed  by  a  more  or 
less  complex  circular  or  spiral  wreath  of  long,  powerful,  cirrose 
cilia,  the  left  limb  or  extremity  of  which  is  spirally  involute 
and  forms  the  entrance  to  the  oral  fossa.  This  fossa  is  con- 
tinued as  a  short,  tubular  pharynx.  Anus  posteriorly  situated, 
subterminal.  Cuticular  cilia  very  fine,  distributed  evenly 
throughout,  clothing  both  the  body  and  the  retractile  pedicle. 
Length  of  lorica  80  to  150  yu.  There  are  many  species,  vary- 
ing greatly  in  the  size  and  shape  of  the  loricae.  In  the  fresh- 
water forms  the  lorica  is  generally  cylindrical.  Another 
genus,  Tintinnidium,  varies,  from  Tintinnus  only  in  having  a 
more  mucilaginous  sheath  and  in  being  permanently  attached 
to  foreign  objects.  (PI.  XIII,  Fig.  12.) 

Codonella. 

Animalcules  conical  or  trumpet-shaped,  solitary,  free-swim- 
ming, highly  contractile,  inhabiting  a  helmet-  or  bell-shaped 
lorica,  to  which  they  are  attached  by  their  posterior  extremity. 
The  anterior  region  truncate  or  excavate,  forming  a  circular 
peristome  having  an  outer  fringe  of  about  twenty  long,  ten- 
tacle-like cilia,  and  an  inner  collar-like  border,  or  frill,  which 
bears  an  equal  number  of  slender,  lappet-like  appendages. 
Entire  cuticular  surface  clothed  with  fine,  vibratile  cilia. 
Lorica  not  perforated,  of  chitinous  consistence,  often  of  a 
brown  color,  sometimes  sculptured  or  mixed  with  foreign 
granular  substances.  Length  of  lorica  50  to  150  JJL.  Several 
species,  mostly  marine.  (PI.  XIV,  Fig.  i.) 

Stentor. 

Animalcules  sedentary  or  free-swimming  at  will ;  bodies  highly 
elastic  and  variable  in  form  :  when  swimming  and  contracted, 
clavate,  pyriform,  or  turbinate  ;  when  fixed  and  extended, 
trumpet-shaped,  broadly  expanded  anteriorly,  tapering  off  arid- 
attenuated  towards  the  attached  posterior  extremity.  Peristome 


244  THE   MICROSCOP  Y   OF  DRINKING-  WA  TER. 

describing  an  almost  complete  circuit  around  the  expanded 
anterior  border,  its  left-hand  extremity  or  limb  spirally  in- 
volute, forming  a  small  pocket-shaped  fossa  conducting  to  the 
oral  aperture,  the  right-hand  limb  free  and  usually  raised  con- 
siderably above  the  opposite  or  left-hand  one.  Peristomal 
cilia  ,  cirrose,  very  large  and  strong;  cilia  of  the  cuticular 
surface  very  fine,  distributed  in  even  longitudinal  rows,  oc- 
casionally supplemented  by  scattered  hair-like  setae.  Nucleus 
band-like,  moniliform,  or  rounded.  Contractile  vesicle  com- 
plex. Multiplication  by  oblique  fission  and  by  germs  separated 
from  the  band-like  endoplast.  There  are  many  species,  some 
of  large  size,  colorless,  or  greenish,  bluish,  brownish,  etc. 
(PL  XIV,  Fig.  2.) 
Bursaria. 

Animalcules  free-swimming,  broadly  ovate,  somewhat  flattened 
on    one    side,    anteriorly    truncate.       Peristome-field    pocket- 

•''  shaped,  deeply  excavate,  situated  obliquely  on  the  anterior 
half  of  the  body,  having  a  broad  oral  fossa  in  front,  and  a  cleft- 
like  lateral  fissure,  which  extends  from  the  left  corner  of  the 
contour  border  to  the  middle  of  the  ventral  side  ;  no  tremulous 

-t"*  flap.  Pharynx  long,  funicular,  bent  towards  the  left,  and 
forming  a  continuation  of  the  peristome  excavation.  Adoral 
ciliary  wreath  broad,  much  concealed,  lying  completely  within 
the  peristome-cleft.  Cuticular  cilia  fine,  in  longitudinal  rows. 
Anus  posteriorly  situated,  terminal.  Nucleus  band-like,  curved, 
or  sinuous.  Contractile  vesicles  distinct,  usually  multiple,, 
Few  species.  Length  300  to  500  yw.  (PI.  XIV,  Fig.  3.) 

ORDER  HOLOTRICHA. 

Ciliata  with  but  one  sort  of  cilia,  these  covering  the  body 
uniformly  and  almost  completely.  A  variously  modified 
extensile  or  undulating  membrane  sometimes  present.  Oral 
~nd  anal  orifices  usually  conspicuous.  Trichocysts  sometimes 
present  in  the  cuticular  layer. 


Animalcules  free  -swimming,  ovate  or  elongate,  asymmetrical, 


PROTOZOA.  245* 

more  or  less  flexible,  but  persistent  in  shape.  Finely  ciliated 
throughout,  the  cilia  of  the  oral  region  not  differing  in  size  or 
character  from  those  of  the  general  surface  of  the  body.  An- 
oblique  groove  developed  on  the  ventral  surface,  at  the  pos- 
terior extremity  of  which  is  situated  the  oral  aperture.  Cor- 
tical layer  usually  enclosing  trichocysts.  Contractile  vesicles 
and  nucleus  conspicuous,  the  former  sometimes  stellate. 
There  are  several  species.  The  most  important  is  P.  aurelia, 
which  is  often  found  in  sewage-polluted  and  stagnant  water. 
It  is  colorless,  has  a  length  of  about  225  jw,  and  moves  with  a 
brisk  rotatory  motion.  (PI.  XIV,  Fig.  4.) 

Nassula  .•.  ?\ 

Animalcules  ovate,  cylindrical,  flexible,  but  not  polymorphic, 
usually  highly  colored — rose,  red,  blue,  yellow,  etc.  Oral 
aperture  lateral.  Pharynx  armed  with  a  simple  horny  tube  or 
with  a  cylindrical  fascicle  of  rod-like  teeth.  Entire  surface  of 
cuticle  finely  and  evenly  ciliate.  The  cortical  layer  sometimes 
containing  trichocysts.  There  are  several  species,  varying  in 
color,  shape,  and  size.  Length  50  to  250  //.  (PP.  XIV, 

Fig-  5-) 
Coleps. 

Animalcules  ovate,  cylindrical,  or  barrel -shaped,  persistent  in 
shape,  cuticular  surface  divided  longitudinally  and  trans- 
versely by  furrows  into  quadrangular  facets ;  these  facets  are 
smooth  and  indurated,  the  narrow  furrows  soft  and  clothed 
with  cilia ;  the  anterior  margin  mucronate  or  denticulate ; 
the  posterior  extremity  mucronate  and  provided  with  spines  or 
cusps.  Oral  aperture  apical,  terminal,  surrounded  with  cilia^ 
Anal  aperture  at  posterior  extremity.  Color  gray  or  light 
brown.  The  most  common  species  is  C.  hirtus,  which  has  a 
length  of  about  60  p.  (PI.  XIV,  Fig.  6.) 
Enchelys. 

Animalcules  free-swimming,  elastic,  and'  changeable  in  shape, 
pyriform  or  globose.  Oral  aperture  situated  at  the  termination 
of  the  narrower  and  usually  oblique  truncate  anterior  extremity. 
Anal  aperture  at  the  posterior  termination.  Cuticular  surface 
finely  and  entirely  ciliate ;  the  cilia  are  longer  in  the  region 


246  THE   MICROSCOPY   OF  DRINKING-WATER. 

of  the  mouth.  Few  species.  Length  about  25  to  50  /*. 
(PI.  XIV,  Fig.  7.). 

Trachelocerca. 

Animalcules  colorless,  highly  elastic,  and  changeable  in  form, 
the  anterior  porlion  produced  as  a  long,  flexible,  narrow,  neck- 
like  process,  the  apical  termination  of  which  is  separated  by  an 
annular  constriction  from  the  preceding  part,  and  is  perforated 
apically  by  the  oral  aperture.  Cuticular  surface  evenly  and 
finely  ciliate  ;  a  circle  of  larger  cilia  developed  around  the  oral 
region.  Length  of  extended  body  about  150  fit.  Few  species. 
(PL  XIV,  Fig.  8.) 

Pleuronema. 

Animalcules  ovate,  colorless.  Oral  aperture  situated  in  a 
depressed  area  near  the  centre  of  the  ventral  surface,  supple- 
mented by  an  extensile,  hood-shaped,  transparent  membrane 
or  velum,  which  is  let  down  or  retracted  at  will.  Numerous 
longer  vibratile  cilia  stationed  at  the  entrance  of  the  oral  cavity. 
The  general  surface  of  the  body  clothed  with  long,  stiff,  hair- 
like  setae.  The  cortical  layer  usually  containing  trichocysts. 
Length  60  to  ioo//.  Few  species.  (PI.  XIV,  Fig.  9.) 

Colpidium. 

Animalcules  free-swimming,  colorless,  kidney -shaped.  Entirely 
ciliate.  Oral  aperture  inferior,  subterminal.  Pharynx  sup- 
ported throughout  its  length  by  an  undulating  membrane  which 
projects  exteriorly  in  a  tongue-like  manner.  Two  nuclei, 
rounded,  sub-central.  Length  50  to  100  //.  One  species. 
(PI.  XV,  Fig.  i.) 

SUB-CLASS  SUCTORIA  (TENTACULIFERA  OR  ACINETARIA). 

Protozoa  with  neither  flagellate  appendages  nor  cilia  in 
their  adult  state,  but  seizing  their  food  and  effecting  locomo- 
tion, when  unattached,  by  means  of  tentacles.  These  are 
simply  adhesive  or  tubular  and  provided  at  their  distal 
extremity  with  a  cup-like  sucking-disk.  Nucleus  usually 
much  branched.  One  or  more  contractile  vesicles.  Multi- 
plication by  longitudinal  or  transverse  fission  or  by  external 


PROTOZOA.  247 

or  internal  bud-formation.      The  young    forms    are  ciliated. 
Most  of  the  Suctoria  are  sedentary. 

Acineta. 

Animalcules  solitary,  ovate  or  elongate,  secreting  a  protective 
lorica,  to  the  sides  of  which  they  are  adherent  or  within  which 
they  may  remain  freely  suspended.  Lorica  transparent,  tri- 
angular or  urn-shaped,  supported  upon  a  rigid  pedicle.  Ten- 
tacles suctorial,  capitate,  distributed  irregularly  or  in  groups. 
There  are  many  species.  (PL  XV,  Fig.  2.) 


CHAPTER  XXL 
ROTIFERA. 

THE  Rotifera,  or  Rotatoria,  comprise  a  well-defined  group 
of  minute  multicellular  animals.  They  are  often  included 
among  the  Vermes,  but  some  of  them  possess  characteristics 
that  suggest  the  Arthropoda. 

Though  microscopic  in  size,  the  Rotifera  are  quite  highly 
organized.  They  have  a  well-defined  digestive  system,  in- 
cluding a  mouth,  or  buccal  orifice;  a  mastax,  a  peculiar  set 
of  jaws  for  mastication;  salivary  glands;  an  oesophagus; 
gastric  glands;  a  stomach;  an  intestine;  and  an  anus.  There 
is  a  vascular  system,  a  muscular  system,  and,  it  is  claimed,  a 
nervous  system.  There  is  a  conspicuous  reproductive  system, 
and  both  males  and  females  are  observed,  although  the  males 
are  rare.  The  transparency  of  most  of  the  Rotifera  renders 
these  various  organs  subjects  of  easy  investigation. 

The  organisms  are  protected  by  a  firm,  homogeneous, 
structureless  cuticle,  often  hardened  by  a  development  of 
chitin,  forming  a  carapace  or  lorica.  Some  genera  are  further 
protected  by  an  exterior  casing  or  sheath,  called  an  '*  urceo- 
lus,"  which  may  be  gelatinous  and  transparent,  as  in  Floscu- 
laria,  or  covered  with  foreign  particles  or  pellets,  as  in 
Melicerta. 

The  Rotifera  are  generally  bilaterally  symmetrical,  with  a 
dorsal  and  ventral  surface,  with  definite  head  region  and  tail 

248 


RO  TIFERA.  249 

region,  broadest  anteriorly  and  tapering  posteriorly.  There 
are  three  features  of  the  Rotifera  that  deserve  special  atten- 
tion, partly  because  they  are  unique  in  the  organisms  of  this 
group  and  partly  because  they  are  used  as  the  basis  of  classi- 
fication. They  are  the  ciliary  wreath,  the  mastax,  and  the 
foot. 

The  ciliary  wreath  consists  of  one  or  more  circlets  of  cilia 
springing  from  disc-like  lobes  surrounding  the  mouth  at  the 
anterior  end.  By  their  continual  lashing  they  present  the 
appearance  of  wheels,  giving  to  these  organisms  the  name  of 
"wheel-animalcules."  Their  function  is  to  assist  in  locomo- 
tion, to  create  currents  in  the  water  by  which  food-particles 
are  carried  into  the  mouth,  and  to  conduct  this  food-material 
through  the  alimentary  canal.  The  disc-like  lobe  bearing  the 
cilia  is  known  by  the  names  of  corona,  trochal  disc,  or  velum. 
It  takes  different  shapes  in  different  rotifers.  Its  simplest 
form  is  an  oval  or  circle.  In  more  complex  forms  it  is 
intricately  folded,  as  shown  on  PL  XVI,  Figs.  A  to  E.  The 
ciliated  wreath  is  often  supplemented  by  certain  projecting 
processes,  ciliated  or  bearing  setae  or  bristles. 

The  foot,  pseudopodium,  or  posterior  extremity  of  a  rotifer 
presents  several  different  types.  It  may  be  fleshy  and 
transversely  wrinkled,  or  hard  and  jointed;  it  maybe  non- 
retractile  or  retractile;  often  the  jointed  forms  are  telescopic; 
it  may  terminate  in  a  sort  of  sucking-disc  or  in  a  ciliated 
expansion,  or  it  may  be  furcate,  or  divided  into  toes,  as 
shown  on  PL  XVI,  Figs.  F  to  I.  In  some  species  the  foot 
is  altogether  lacking. 

The  mastax  is  a  sort  of  muscular  bulb  forming  a  part  of 
the  pharynx  and  containing  the  trophi.  It  has  an  opening 
above  from  the  mouth  and  below  into  the  oesophagus.  The 
trophi,  or  teeth,  are  peculiar  calcareous  structures.  Their 


250  THE   MICROSCOPY   OF  DRINKING-WATER. 

function  is  to  grind  the  food  before  it  passes  into  the  stomach, 
and  this  grinding  movement  may  be  witnessed  through  the 
transparent  walls  of  many  rotifers.  The  trophi  consist  of  two 
toothed,  hammer-like  bodies,  or  mallei,  that  pound  on  a  sort 
of  split  anvil,  or  incus.  The  malleus  consists  of  an  upper 
part,  the  head  or  uncus,  and  a  lower  part,  the  handle  or 
manubrium.  The  incus  also  consists  of  two  parts,  a  sym- 
metrically divided  upper  part,  the  rami,  that  receives  the 
blow  of  the  malleus,  and  a  lower  part  or  fulcrum.  The 
trophi  show  great  modifications  in  different  genera  in  the 
shape  and  proportion  of  the  various  parts.*  PI.  XVI,  Fig. 
J  represents  a  typical  form. 

These  three  characteristics — the  arrangement  of  the  ciliary 
wreath,  the  structure  of  the  foot,  and  the  form  of  the  trophi 
— serve  as  the  basis  for  dividing  the  Rotifera  into  orders  and 
families.  The  following  classification  is  that  adopted  by 
Hudson  and  Gosse.  Only  the  typical  and  very  common 
genera  are  described. 

*  The  following  terms  are  used  to  describe  the  trophi  (see  PI.  XVI, 
Figs.  J  to  P)  : 

Malleate. — Mallei  stout  ;  manubria  and  unci  of  nearly  equal  length  ; 
unci  5-  to  7-toothed  ;  fulcrum  short. 

Submalleate. — Mallei  slender  ;  manubria  about  twice  as  large  as  the 
unci  ;  unci  3-  to  5-toothed. 

Forcipitate. — Mallei  rod-like  ;  manubria  and  fulcrum  long  ;  unci  pointed 
or  evanescent  ;  rami  much  developed  and  used  as  forceps. 

Incudate. — Mallei  evanescent  ;  rami  highly  developed  into  a  curved 
forceps  ;  fulcrum  stout. 

Uncinate. — Unci  2-toothed  ;  manubria  evanescent  ;  incus  slender. 

Ramate. — Rami  subquadrate,  each  crossed  by  two  or  three  teeth  ; 
manubria  evanescent  :  fulcrum  rudimentary. 

Malleo-ramate. — Mallei  fastened  by  unci  to  rami  ;  manubria  three  loops 
soldered  to  the  unci  ;  unci  3-toothed  ;  rami  large,  with  many  striae  parallel 
to  the  teeth  ;  fulcrum  slender. 


ROTIFERA.  251 

ORDER    RHIZOTA. 

Rotifera  fixed  when  aciult;  usually  inhabiting  a  gelatinous 
tube  excreted  from  the  skin.  Foot  transversely  wrinkled, 
not  contractile  within  the  body,  ending  in  an  adhesive  suck- 
ing-disc or  cup,  without  telescopic  joints,  never  furcate. 

FAMILY   FLOSCULARIAD/E. — Corona   produced    longitudinally  into 
lobes  bearing  the  setae.      Mouth  central.      Ciliary  wreath  a  single  half- 
circle  above  the  mouth.     Trophi  uncinate. 
Floscularia. 

Frontal  lobes  short,  expanded,  or  Wholly  wanting.  Setae  very 
long  and  radiating,  or  short  and  cilia-like.  Foot  terminated 
by  a  non-retractile  peduncle,  ending  in  an  adhesive  disc. 
Inhabiting  a  transparent  gelatinous  tube  into  which  the  animal 
contracts  when  alarmed.  There  are  several  species,  varying 
in  length  from  200  to  2500  //.  (PL  XV,  Fig.  3.) 

FAMILY  MELICERTAD^E. — Corona  not  produced  in  lobes  bearing 
setae.  Mouth  lateral.  Ciliary  wreath  a  marginal  continuous  curve  bent 
on  itself  at  the  dorsal  surface  so  as  to  encircle  the  corona  twice,  with 
the  mouth  between  its  upper  and  lower  curves,  and  having  a  dorsal 
gap  between  its  points  of  flexure.  Trophi  malleo-ramate. 
Melicerta. 

Corona    of  four   lobes.      Dorsal    gap   wide.     Dorsal  antennae 
minute.     Ventral  antennae  obvious.     Inhabiting  tubes  built  up 
of  pellets.      Length  800  to  1500  //.     Few  species.     M.  ringens 
is  very  common  on  water-plants.      (PI.  XV,  Fig.  4. ) 
Conochilus. 

Corona  horseshoe-shaped,  transverse ;  gap  in  ciliary  wreath 
ventral.  Mouth  on  the  corona,  and  towards  its  dorsal  side. 
Dorsal  antennae  very  minute  or  absent.  Ventral  antennae  obvi- 
ous. Forming  free-swimming  clusters  of  several  individuals, 
inhabiting  coherent  gelatinous  tubes.  Length  500  to  1200  //. 
Two  species.  C.  volvox  is  very  common.  (PI.  XV,  Fig.  5.) 


2$2  THE   MICROSCOPY   OF  DRINKING-WATER. 

ORDER   BDELLOIDA. 

Rotifera  that  swim  with  their  ciliary  wreath  and  creep  like 
a  leech.  Foot  wholly  retractile  within  the  body,  telescopic, 
at  the  end  almost  invariably  divided  into  three  toes. 

FAMILY  PHILODINAD^E. — Corona  a  pair  of  circular  lobes  transversely 
placed.  Ciliary  wreath  a  marginal  continuous  curve  bent  on  itself  at 
the  dorsal  surface  so  as  to  encircle  the  corona  twice,  with  mouth 
between  its  upper  and  lower  curves,  and  having  also  two  gaps,  the  one 
dorsal  between  its  points  of  flexure,  the  other  ventral  in  the  upper 
curve  opposite  to  the  mouth.  Trophi  ramate. 
Rotifer. 

Eyes  two,  within  the  frontal  column.  The  most  common 
species  is  R.  vulgaris,  which  has  a  white  body,  smooth,  and 
tapering  to  the  foot.  Spurs  and  dorsal  antennae  of  moderate 
length.  Length  about  500  jn.  This  was  one  of  the  first 
rotifers  discovered.  It  gave  its  name  to  the  entire  class.  (PL 
XV,  Fig.  6.) 

ORDER   PLOIMA. 

Rotifera  that  swim  with  their  feet  and  (in  some  cases) 
creep  with  their  toes.  This  is  the  largest  and  most  important 
order  of  Rotifera. 

SUB-ORDER  ILLORICATA. 

Integument  flexible,  not  stiffened  to  an  enclosing  shell. 
Foot,  when  present,  almost  invariably  furcate,  but  not  trans- 
versely wrinkled;  rarely  more  than  feebly  telescopic,  and 
partially  retractile. 

FAMILY  MICROCODID^E. — Corona  obliquely  transverse,  flat,  circular. 
Mouth  central.      Ciliary  wreath  a  marginal  continuous  curve  encircling 
the  corona,  and  two  curves  of  larger  cilia,  one  on  each  side  of  the 
mouth.     Trophi  forcipitate.     Foot  stylate. 
Microcodon. 

Eye   single,   centrally  placed,  just   below   the  corona.     One 


ROTIFERA.  253 

species.  Length  about  200  /*,  of  which  the  foot  is  more 
than  half.  (PL  XV,  Fig.  7.) 

FAMILY  ASPLANCHNAD^E. — Corona   subconical,    with  one  or  two 
apices.      Ciliary   wreath   single,   edging    the   corona.     Intestine   and 
cloaca  absent. 
Asplanchna. 

Corona   with    two   apices.       Trophi    incudate,    not    enclosed 

within    a   mastax.       Stomach    of  moderate   size,    spheroidal. 

Viviparous.       Several  species.      Very  large   and   transparent. 

(PL  XV,  Fig.  8.) 

FAMILY  SYNCH^ETAD^E. — Corona  a  transverse  spheroidal  segment, 
sometimes  much  flattened,  with  styligerous  prominences.  Ciliary 
wreath  a  single  interrupted  or  continuous  marginal  curve  encircling 
the  corona.  Mastax  very  large,  pear-shaped.  Trophi  forcipitate. 
Foot  minute,  furcate. 
Synchaeta. 

Form  usually  that  of  a  long  cone  whose  apex  is  the  foot ;  front 
furnished  with  two  ciliated  club-shaped  prominences.  Ciliary 
wreath  of  interrupted  curves.  Foot  minute,  furcate.  Several 
species.  Length  150  to  300  //.  (PL  XVI,  Fig.  i.) 

FAMILY  TRIARTHRAD^. — Body  furnished  with  skipping  append- 
ages.     Corona  transverse.     Ciliary  wreath    single,    marginal.     Foot 
absent. 
Polyarthra. 

Eye  single,   occipital.      Mastax  very  large   and   pear-shaped. 
Trophi  forcipitate.      Provided  with  two  clusters  of  six  spines 
on  the  shoulders,  the  spines  being  in  the  form  of  serrated  blades. 
Length  about  125  /*.      (PL  XVI,  Fig.  2.) 
Triarthra. 

Eyes  two,  frontal.  Mastax  of  moderate  size.  Trophi  malleo- 
ramate.  Spines  single,  two  lateral,  one  ventral.  There  are 
three  species,  differing  chiefly  in  the  length  of  the  spines. 
In  the  most  common  species  the  spines  are  twice  the  length  of 
the  body.  Length  of  body  about  150  /*.  (PL  XVI,  Fig.  3.) 

FAMILY  HYDATINAD^E. — Corona  truncate,  with  styligerous  prom- 
inences.    Ciliary  wreath  two  parallel  curves,  the  one  marginal  fring- 


254  THE   MICROSCOPY   OF  D  KIN  KING- WATER. 

ing  the  corona  and  mouth,  the  other  lying  within  the  first,  the  stylig- 

erous  prominences  lying  between  the  two.       Trophi  malleate.       Foot 

furcate. 

Hydatina. 

Body  conical,  tapering  towards  the  foot.  Foot  short  and  con- 
fluent with  the  trunk.  Eye  absent.  This  is  one  of  the  largest 
of  the  Ploima.  Length  about  600  ju. 

FAMILY  NOTOMMATAD^E. — Corona  obliquely  transverse.  Ciliary 
wreath  of  interrupted  curves  and  clusters,  usually  with  a  marginal 
wreath  surrounding  the  mouth.  Trophi  forcipitate.  Foot  furcate. 
This  family  is  the  most  typical,  the  most  highly  organized,  of  the 
Rotifera. 
Diglena. 

Body  subcylindrical,  but  very  versatile  in  outline,  often 
swelling  behind  and  tapering  to  the  head.  Eyes  two,  minute, 
situated  near  the  edge  of  the  front.  Foot  furcate.  Trophi 
forcipitate,  generally  protrusile.  Several  species.  Length 
125  to  400  /(.  (PL  XVI,  Fig.  4.) 

SUB-ORDER  LORICATA. 

Integument  stiffened  to  a  wholly  or  partially  enclosing 
shell;  foot  various. 

FAMILY  RATTULID^E. — Body  cylindrical  or  fusiform,  smooth,  with- 
out plicae  or  angles  ;  contained  in  a  lorica  closed  all  around,  but  open 
at  each  end,  often  ridged.     Trophi  long,  asymmetrical.      Eye  single, 
cervical. 
Mastigocerca. 

Body  fusiform  or  irregularly  thick,  not  lunate.     Toe  a  single 
style,  with  accessory  stylets  at  its  base.      Lorica  often  furnished 
*  with  a  thin  dorsal  ridge.      Many  species.      (PL  XVI,  Fig.  5.) 

FAMILY  COLURID^E. — Body  enclosed  in  a  lorica,  usually  of  firm 
consistence,  variously  compressed  or  depressed,  open  at  both  ends, 
closed  dorsally,  usually  open  or  wanting  ventrally.  Head  surrounded 
by  a  chitinous  arched  plate  or  hood.  Toes  two,  rarely  one,  always 
exDOsed. 


ROT  IP  ERA.  255 

Colurus. 

Body  subglobose,  more  or  less  compressed.  Lorica  of  two 
lateral  plates,  open  in  front,  gaping  behind.  Frontal  hood  in 
form  of  a  non-retractile  hook.  Foot  prominently  extruded,  of 
distinct  joints,  terminated  by  two  furcate  toes.  Many  species. 

FAMILY  BRACHIONID^E. — Lorica  box-like,  open  at  each  end,   gen- 
erally armed  with   anterior  and  posterior  spines.      Foot   very  long, 
flexible,  uniformly  wrinkled,  without  articulation;  toes  very  small. 
Brachionus. 

Lorica  without  elevated  ridges,  gibbous  both  dorsally  and  ven- 
trally.     Foot  very  flexible,   uniformly  wrinkled,  without  arti- 
culation ;    toes  very  small.      Free-swimming.      Many  species. 
(PL  XVII,  Fig.  i.) 
Noteus. 

Lorica  facetted  and  covered  with  raised  points ;  gibbous  dor- 
sally, flat  ventrally.  Foot  obscurely  jointed.  Toes  moderately 
long.  Eyes  wanting.  Length  350  jn. 

FAMILY    ANUR^AD/E. — Lorica  box-like,  broadly    open    in   front, 
open  behind  only  by  a  narrow  slit.      Usually  armed   with  spines  or 
elastic  setae.      Foot  wholly  wanting. 
Anuraea 

Lorica  an  oblong  box,  open  widely  in  front,  narrowly  in  rear ; 
dorsal  surface  usually  tessellated.  The  occipital  ridge  always, 
the  anal  sometimes,  furnished  with  spines.  The  egg  after 
extrusion  is  carried  attached  to  the  lorica.  Free-swimming. 
Length  about  125  yu.  (PL  XVII,  Figs.  2  and  3.) 
Notholca. 

Lorica  ovate,  truncate  and  six-spined  in  front,  sometimes  pro- 
duced behind  ;  of  two  spoon-like  plates  united  laterally.  No 
posterior  spines.  Dorsal  surface  marked  longitudinally  with  al- 
ternate ridges  and  furrows.  Expelled  egg  not  usually  carried. 
Free-swimming.  Several  species.  (PL  XVII,  Fig.  4.) 

ORDER   SCIRTOPODA. 

Rotifera  swimming  with  their  ciliary  wreath  and  skipping 
with  arthropodous  limbs;  foot  absent.  There  is  but  one 
genus,  Pedalion,  and  that  is  rare., 


CHAPTER    XXII. 
CRUSTACEA. 

THE  Crustacea  belong  to  the  Arthropoda — that  is,  to  that 
group  of  the  Articulates  that  have  jointed  appendages.  Most 
of  the  larger  Crustacea  are  marine,  but  many  of  the  smaller 
forms  are  found  in  fresh  water.  These  vary  in  size  from 
objects  barely  visible  to  the  naked  eye  to  bodies  several 
centimeters  in  length.  The  most  common  forms  are  some- 
what less  in  size  than  the  head  of  a  pin. 

The  fresh-water  Crustacea  have  been  sometimes  divided 
into  two  groups,  the  Entomostraca  and  the  Malacostraca. 

The  Malacostraca  are  comparatively  large  forms.  They 
include  the  Amphipoda,  one  of  which  is  Gammarus  pulex, 
the  "water-crab";  the  Isopoda,  with  Asellus  aquaticus, 
or  the  '*  water-louse" ;  and  the  Decapoda,  or  ten- footed 
animals. 

The  Entomostraca  may  be  said  to  include  most  of  the 
smaller,  free-swimming  Crustacea,  but  the  word  is  sometimes 
used  in  a  stricter  and  more  limited  sense.  The  bodies  of  the 
Entomostraca  are  more  or  less  distinctly  jointed,  and  are  con- 
tained in  a  horny,  leathery,  or  brittle  shell,  formed  of  one  or 
more  parts.  The  shell  is  composed  of  chitin  impregnated 
with  a  variable  amount  of  carbonate  of  lime.  It  is  often  trans- 
parent, and  may  be  striated,  reticulated,  notched,  spinous, 
etc.  It  varies  in  structure  in  different  genera.  It  may  be  a 

256 


CRUSTACEA.  2  57 

bivalve,  like  a  mussel-shell,  or  folded  so  as  to  give  the  appear- 
ance of  a  bivalve  without  being  really  so,  or  segmented,  like  a 
lobster's  shell.  The  body  of  the  organism  is  segmented,  and 
there  is  generally  a  cephalo-thorax  region  and  an  abdominal 
region.  In  some  cases  there  are  distinct  head  and  tail 
regions.  There  are  one  or  two  pairs  of  antennae  springing 
from  near  the  head.  The  feet  vary  in  number,  position,  and 
character.  In  some  genera  they  are  flattened  and  have 
branchiae,  or  breathing-plates,  attached  to  them,  enabling  them 
to  perform  the  function  of  respiration.  There  is  one  conspic- 
uous eye,  usually  black  or  reddish,  situated  in  the  head 
region.  Near  the  mouth  are  two  mandibles,  and  near  them 
are  the  maxillae,  or  foot-jaws,  armed  with  spines  or  claws  arid 
sometimes  with  branchiae.  There  is  a  heart,  often  square, 
that  causes  the  circulation  of  colorless  blood;  and  well-marked 
digestive,  muscular,  nervous,  and  reproductive  systems.  The 
eggs  of  the  Entomostraca  may  be  seen  in  brood-cavities  inside 
the  shell  or  in  exterior  attached  egg-sacs.  The  young  often 
hatch  in  the  nauplius  form,  and  undergo  several  changes 
before  arriving  at  the  adult  condition. 

The  Entomostraca  are  usually  divided  into  four  orders — 
Copepoda,  Ostracoda,  Cladocera,  and  Phyllopoda.  The  last 
three  are  sometimes  placed  as  sub-orders  under  the  order 
Branchiopoda. 

ORDER  COPEPODA. 

Shell  jointed,  forming  a  more  or  less  cylindrical  buckler, 
or  carapace,  enclosing  the  head  and  thorax.  The  anterior 
part  of  the  body  is  composed  of  ten  segments  more  or  less 
fused.  The  five  constituting  the  head  bear  respectively  a 
pair  of  jointed  antennae,  a  pair  of  branched  antennules,  a  pair 
of  mandibles,  or  masticatory  organs,  a  pair  of  maxillae,  and  a 


258  THE   MICROSCOPY   OF  DRINKING-WATER. 

pair  of  foot-jaws.  The  five  thoracic  segments  bear  five  pairs 
of  jointed  swimming-feet,  the  fifth  often  rudimentary.  There 
are  about  five  abdominal  segments,  nearly  devoid  of  append- 
ages, and  continued  posteriorly  by  two  tail-like  stylets. 
Young  hatched  in  the  nauplius  state. 

The  Copepoda  move  by  vigorous  leaps.  They  lead  a 
roving,  predatory  life  and  well  deserve  the  name  of  "scav- 
engers." 

Cyclops. 

Copepoda  with  head  hardly  distinguishable  from  the  body. 
The  thorax  and  abdomen  generally  distinguishable,  the  former 
having  four  and. the  latter  six  segments.  Two  pairs  of  antennae, 
the  superior  large  and  many-jointed,  the  inferior  smaller,  fur- 
nished with  short  setae ;  both  superior  antennas  of  the  male 
have  swollen  joints.  The  antennae  assist  in  locomotion. 
Two  pairs  of  vigorous  branched  foot-jaws.  One  eye,  large, 
single,  central.  Two  egg-sacs.  Cyclops  are  very  prolific, 
as  many  as  30  or  40  ova  being  laid  at  a  time  and  broods  oc- 
curring at  short  intervals.  The  eggs  may  hatch  after  leaving 
the  ovary.  There  are  many  species.  (PI.  XVII,  Fig.  5.) 

Dlaptomus. 

Copepoda  resembling  Cyclops  in  their  general  appearance. 
Thorax  and  abdomen  each  five-segmented.  Antennae  very 
long,  many-jointed,  with  setae ;  the  right  antenna  only  swollen 
in  the  male.  Antennules  large,  bifid,  the  two  unequal  branches 
arising  from  a  common  footstalk.  Three  pairs  of  unbranched 
foot -jaws.  One  egg-sac.  The  ova  hatch  while  borne  by  the 
female.  (PI.  XVII,  Fig.  6.) 

Canthocamptus 

Copepoda  somewhat  resembling  Cyclops.  The  ten  segments 
of  the  thorax  and  abdomen  not  distinguishable.  The  seg- 
ments decrease  in  size  as  they  descend.  At  the  junction  of 
the  fourth  and  fifth  segments  the  body  is  very  movable. 
Antennae  very  short.  Five  pairs  of  swimming-feet,  much 
longer  than  in  cyclops.  One  egg-sac.  (PI.  XVII,  Fig.  7.) 


CRUSTACEA.  259 

I 

ORDER   OSTRACODA. 

Shell  consisting  of  two  valves,  entirely  enclosing  the  body; 
from  one  to  three  pairs  of  feet;  no  external  ovary. 

Cypris. 

Body  enclosed  within  a  horny  bivalve  shell,  oval  or  remform. 
Superior  antennae  seven-jointed,  with  long  feathery  filaments 
arising  from  the  last  three.  Inferior  antennae  leg-like,  with 
claws  and  setae  at  the  end.  Two  pairs  of  feet.  Eye  single. 
Color  greenish,  brownish,  or  whitish.  A  large  number  of 
species.  The  shell  is  seldom  open  wide.  (PL  XVII,  Fig.  8.) 

ORDER    CLADOCERA. 

Shell  consisting  of  two  thin  chitinous  plates  springing  from 
the  maxillary  segment.  The  most  important  characteristic  is 
the  presence  of  several  pairs  of  leaf-like  feet  provided  with 
branchiae,  or  breathing-organs.  There  is  a  large  single  eye. 
Two  pairs  of  antennae,  large,  branched,  and  adapted  for. 
swimming.  This  order  contains  a  number  of  common  genera. 

Daphnia. 

Head  produced  into  a  prominent  beak ;  valves  of  the  carapace 
oval,  reticulated,  and  terminated  below  by  a  serrated  spine. 
Superior  antennae  situated  beneath  the  beak,  one-jointed  or 
as  a  minute  tubercle  with  a  tuft  of  setae.  Inferior  antennae 
large  and  powerful,  two-branched,  one  branch  three-jointed, 
the  other  four-jointed.  Five  pairs  of  legs.  Heart  a  colorless 
organ  at  the  back  of  the  head.  Eye  spherical,  with  numerous 
lenses.  Ova  carried  in  a  cavity  between  the  back  of  the 
animal  and  the  shell.  At  certain  seasons  "  winter  eggs  "  are 
produced.  Daphnia  move  with  a  louse-like,  skipping  move- 
ment. They  are  sometimes  called  ' 'arborescent  water-fleas. " 
There  are  numerous  species.  (PI.  XVII,  Fig.  9.) 
Bosmina. 

Head  terminated  in  front  by  a  sharp  beak  directed  forwards 
and  downwards,  and  from  the  end  of  which  project  the  long, 


260  THE   MICROSCOPY   OF  DRINKING-WATER. 

many-jointed,  curved,  and  cylindrical  superior  antennae.  In- 
ferior antennae  two-branched,  one  branch  three-,  the  other 
four-jointed.  Five  pairs  of  legs.  Shell  oval,  with  a  spine 
at  the  lower  angle  of  the  posterior  border.  Eye  large. 
Eggs  hatched  in  a  brood-cavity  at  the  back  of  the  shell.  (PI. 
XVII,  Fig.  10.) 

Sida. 

Shell  long  and  narrow.  Head  separated  from  the  body  by  a 
depression.  Posterior  margin  nearly  straight.  No  spine  or 
tooth.  Antennae  large,  one  two-jointed,  one  three-jointed. 
Six  pairs  of  legs.  (PI.  XVIII,  Fig.  i.) 

Chydorus. 

Shell  nearly  spherical ;  beak  long  and  sharp,  curved  down- 
wards and  forwards.  Antennae  short.  Eye  single.  Color 
greenish  or  dark  reddish.  Moves  with  an  unsteady  rolling 
motion.  (PL  XVIII,  Fig.  2.) 

ORDER   PHYLLOPODA. 

Body  with  or  without  a  shell.      Legs  1 1  to  60  pairs;  joints 
foliaceous  or  branchiform,  chiefly  adapted  for  respiration  and 
not    motion.     Two    or    more    eyes.     One    or    two    pairs    of 
antennae,  neither  adapted  for  swimming. 
Branchipus. 

Body  without  a  shell.  Legs  eleven  pairs.  Antennae  two 
pairs,  the  inferior  horn-like  and  with  prehensile  appendages  in 
the  male.  Tail  formed  of  two  plates.  Cephalic  horns,  with 
fan-shaped  appendages  at  the  base.  Color  reddish.  Floats 
slowly  on  its  back.  (PL  XVIII,  Fig.  3.) 


CHAPTER  XXIII. 
BRYOZOA,   OR   POLYZOA. 

THE  Bryozoa,  or  Polyozoa,  are  minute  animals  forming 
moss-like  or  coral-like  calcareous  or  chitinous  aggregations. 
The  colonies  are  called  corms,  polyzoaria,  or  ccencecia.  They 
often  attain  an  enormous  size.  In  the  adult  stage  they  lead 
a  sedentary  life  attached  to  some  submerged  object.  The 
animals  themselves  are  small,  but  easily  visible  to  the  naked 
eye.  Some  of  them  are  covered  with  a  secreted  coating, 
or  sheath,  that  takes  the  form  of  a  narrow,  brown-colored 
tube;  others  are  embedded  in  a  mass  of  jelly.  The  genera 
that  live  in  the  brown,  horny  tubes  form  tree-like  growths 
that  often  attain  considerable  length.  The  branches  are 
sometimes  an  inch  long,  and  each  one  is  the  home  of  an 
individual  polyzoon,  or  polypid.  The  branches,  or  hollow 
twigs,  are  separated  from  the  main  stalk  by  partitions,  so 
that,  to  a  certain  extent,  each  polypid  lives  a  separate 
existence  in  its  own  little  case,  though  each  was  formed  from 
its  next  lower  neighbor  by  a  process  of  budding. 

The  body  of  the  organism  is  a  transparent  membranous 
sac,  immersed  in  the  jelly  or  concealed  in  the  brown  opaque 
sheath.  It  contains  a  U-shaped  alimentary  canal,  with  a  con- 
tractile oesophagus,  a  stomach,  and  an  intestine;  a  muscular 
system  that  permits  some  motion  within  the  case,  and  that 
enables  the  animal  to  protrude  itself  from  the  case  and  to 

261 


262  THE   MICROSCOPY   OF  DRINKING-WATER. 

extend  and  contract  its  tentacles;  mesenteries  in  the  form  of 
fibrous  bands;  an  ovary;  and  a  rudimentary  nervous  system. 
There  is  no  heart  and  no  blood-vessels  of  any  kind. 

The  most  conspicuous  part  of  the  animal  is  the  circlet  of 
ciliated  tentacles.  They  are  mounted  on  a  sort  of  platform, 
or  disc,  called  a  lophophore,  at  the  forward  end  of  the  body. 
This  lophophore,  with  its  crown  of  tentacles,  may  be  pro- 
truded from  the  end  of  the  protective  tube  at  the  will  of  the 
animal.  The  tentacles  themselves  may  be  expanded,  giving 
a  beautitul  bell-shaped,  flower-like  appearance.  They  are 
hollow  and  are  covered  with  fine  hair-like  cilia.  They  are 
muscular  and  can  be  bent  and  straightened  at  will.  By  their 
combined  action  currents  in  the  water  are  set  up  towards  the 
mouth,  situated  just  beneath  the  lophophore.  Minute  organ- 
isms are  thus  swept  in  as  food. 

The  Bryozoa  increase  by  a  process  of  budding  which  gives 
rise  to  the  branched  stalks.  There  is  also  a  sexual  reproduc- 
tion. Statoblasts,  or  winter  eggs,  form  within  the  body  and 
escape  after  the  death  of  the  animal.  They  are  sometimes 
formed  in  such  abundance  as  to  form  patches  of  scum  upon  the 
surface  of  a  pond.  The  various  forms  of  these  statoblasts 
assist  in  the  classification  of  the  Bryozoa. 

The    following    are    some   of    the    important   fresh-water 
genera.      There  are  many  marine  forms. 
Plumatella. 

Zoary  confervoid,  brown-colored,  branched,  tubular,  branches 
distinct.  Lophophore  crescent-shaped.  Tentacles  numerous, 
arranged  in  a  double  row.  Statoblasts  elliptical,  with  a  cel- 
lular dark-brown  annulus,  but  no  spines.  (PL  XVIII,  Fig.  6.) 
Fredericella. 

Zoary  tubular,  branched,  brown-colored.  Lophophore  cir- 
cular. Tentacles  about  24,  arranged  in  a  single  row.  Stato- 
blasts elliptical  or  subsph^rical,  smooth,  no  spines,  without  a 
cellular  annulus.  (PI.  XVIII,  Fig.  4.) 


BRYOZOA.  263 

Paludicella. 

Zoary  tubular,  diffusely  branched,  having  the  appearance  of 
brown  club-shaped  cells  joined  end  to  end ;  apertures  lateral, 
near  the  broad  ends  of  the  cells.  Lophophore  circular.  Ten- 
tacles sixteen,  arranged  in  a  single  row.  Statoblasts  elliptical, 
without  spines,  with  a  cellular  bluish-purple  annulus.  (PI. 
XVIII,  Fig.  5.) 

Pectinatella. 

Zoary  massive,  gelatinous,  fixed.  Polypids  protruding  from 
orifices  arranged  irregularly  upon  the  surface.  Tentacles 
numerous.  Statoblasts  circular,  with  a  single  row  of  double 
hooks,  not  forked  at  the  tips,  as  in  Cristatella.  Common. 
(PI.  XVIII,  Fig.  7.) 

Cristatella. 

Zoary  a  mass  of  jelly,  the  polypids  arranged  on  the  outside,  and 
the  tentacles  extended  beyond  the  surface.  The  jelly-mass 
is  usually  long  and  narrow  and  has  the  power  of  moving 
slowly,  creeping  over  submerged  objects.  Tentacles  numer- 
ous, pectinate  upon  two  arms.  Statoblasts  circular,  with  two 
rows  of  double  hooks  having  forked  tips.  Rare. 


CHAPTER    XXIV. 
SPONGID^E. 

THE  fresh-water  sponges  are  not  of  sufficient  importance 
in  water-supplies  to  warrant  an  extended  description  in  this 
work.  They  differ  materially  from  the  marine  sponges,  which 
snake  up  by  far  the  greater  part  of  the  Spongidae. 

The  fresh-water  sponge  is  an  agglomeration  of  animal  cells 
Into  a  gelatinous  mass,  often  referred  to  as  the  "sarcode." 
Embedded  in  the  sarcode  and  supporting  it  are  minute  siliceous 
needles,  or  spicules.  These  skeleton  spicules  interlace  and 
give  the  sponge-mass  a  certain  amount  of  rigidity.  The 
sponge  grows  as  flat  patches  upon  the  sides  of  water-pipes 
and  conduits  and  upon  submerged  objects  in  ponds  and 
streams;  or  it  extends  outward  in  large  masses  or  in  finger- 
like  processes  that  sometimes  branch.  Its  color  when  exposed 
to  the  light  is  greenish  or  brownish,  but  in  the  dark  places  of 
a  water-supply  system  its  color  is  much  lighter  and  is  some- 
times creamy  white.  The  sponge  feeds  upon  the  micro- 
scopic organisms  in  water,  which  are  drawn  in  through  an 
elaborate  system  of  pores  and  canals.  If  these  pores  become 
choked  up  with  silt  and  amorphous  matter  the  organism  dies. 
For  this  reason  sponge-patches  are  more  abundant  upon  the 
top  and  sides  of  a  conduit  than  upon  the,  bottom. 

At  certain  seasons  the  fresh-water  sponges  contain  seed- 

264 


SPONG2D&.  265 

like  bodies  known  under  the  various  names  of  gemmules, 
ovaria,  statoblasts,  statospheres,  winter-buds,  etc.  They  are 
nearly  spherical  and  are  about  0.5  mm.  in  diameter.  They 
have  a  chitinous  coat  that  encloses  a  compact  mass  of  proto- 
plasmic globules.  In  this  coat  there  is  a  circular  orifice, 
known  as  the  foraminal  aperture,  through  which  the  proto- 
plasm bodies  make  their  exit  at  time  of  germination.  In 
most  species  the  chitinous  coat  is  surrounded  by  a  "crust  " 
in  which  are  embedded  minute  spicules,  called  the  "gemmule 
spicules,"  to  distinguish  them  from  the  "skeleton  spicules," 
referred  to  above.  There  is  a  third  kind  of  spicule  known  as 
the  "dermal  spicule"  or  the  "flesh  spicule."  They  lie  upon 
the  outer  lining  of  the  canals  in  the  deeper  portions  of  the 
sponge.  They  are  smaller  than  the  skeleton  spicules  and  are 
not  bound  together.  Dermal  spicules  are'' not  found  in  all 
species. 

The  skeleton  spicules  differ  somewhat  in  different  species. 
They  have  a  length  of  about  250  /*.  They  are  usually  arcuate 
and  pointed  at  the  ends.  They  may  be  smooth  or  covered 
with  spines  (PI.  XVIII,  Figs.  9).  These  skeleton  spicules  of 
sponge  are  commonly  observed  in  the  microscopical  examina- 
tion of  surface-waters.  The  gemmule  spicules  differ  in  char- 
acter in  different  genera  and  species.  Their  characteristics 
are  used  therefore  in  classifying  the  fresh-water  sponges. 

Potts  has  described  a  number  of  different  genera  of  fresh- 
water Spongidae,  among  which  are  Spongilla,  Meyenia, 
Heteromeyenia,  Tubella,  Parmula,  Carterius,  etc.  The  first 
two  are  the  most  important.  They  are  sometimes  given  the 
rank  of  sub-families. 

The  Spongilla  is  a  green,  branching  sponge.  The  skele- 
ton spicules  are  smooth  and  fasciculated.  The  dermal 
spicules  are  fusiform,  pointed,  and  entirely  spined.  The 


266  THE   MICROSCOPY   OF  DRINKING- WATER. 

gemmule  spicules  are  cylindrical,  more  or  less  curved,  and 
sparsely  spined — the  spines  often  recurved.  (PI.  XVIII, 
Fig.  8.) 

The  Meyenia  are  usually  sessile  and  massive.  The  skele- 
ton spicules  are  fusiform-acerate,  abruptly  pointed,  coarsely 
spined  except  near  the  extremities;  spines  subconical,  acute. 
The  dermal  spicules  are  generally  absent.  The  gemmule 
spicules  are  irregular,  birotulate,  vvith  rotules  produced. 


CHAPTER    XXV. 
MISCELLANEOUS  ORGANISMS. 

THE  miscellaneous  higher  animals  and  plants  that  one  is 
likely  to  observe  in  a  microscopical  examination  of  drinking- 
water  are  so  varied,  and  they  are  of  such  little  practical 
importance  in  the  interpretation  of  an  analysis,  that  their 
description  here  is  not  warranted.  It  is  sufficient  to  mention 
the  names  of  a  few  common  forms. 

Of  the  Vermes  the  following  may  be  noted:  Anguillula,  a 
small,  colorless  thread-worm  like  the  vinegar-eel  (PI.  XIX, 
Fig.  i);  Gordius,  the  common  hair-snake;  Nais,  an  annulate 
worm  with  bristles  (PI.  XIX,  Fig.  2);  Tubifex,  another 
bristle-bearing  worm;  Chaetonotus,  an  elongated  worm-like 
organism  with  scales  on  its  back  (PI.  XIX,  Fig.  3).  Of  the 
Arachnida:  Macrobiotus,  the  water-bear  (PI.  XIX,  Fig.  4); 
and  the  Acarina,  water-mites,  or  water-spiders  (PI.  XIX, 
Fig-  5)-  Of  the  Hydrozoa:  the  Hydra,  a  most  interesting 
organism  from  a  zoological  standpoint  (PI.  XIX,  Fig.  6). 
Insect  larvae;  Corethra,  or  the  phantom  larva;  scales  and 
fragments  of  insects;  barbs  of  feathers ;  epithelium-cells;  ova 
of  the  Entozoa,  Crustacea,  Rotifera,  etc. 

Of  the  vegetable  kingdom  may  be  mentioned  Batra- 
chospermum  (PI.  XIX,  Fig.  7);  fragments  of  Sphagnum 
Moss;  Myriophyllum,  or  water-milfoil;  Ceratophyllum,  or 

267 


268  THE   MICROSCOPY   OF  DRINKING-WATER. 

hornwort  (Pi.  XIX,  Fig.  10);  Lemna,  or  duck-weed  (PI. 
XIX,  Fig.  12);  Potamogeton,  or  pond-weed  (PL  XIX,  Fig. 
11);  Hippuris,  or  mare's-tail;  Anacharis,  or  American  water- 
weed  (PL  XIX,  Fig.  9);  Utricularia,  an  insectivorous  plant; 
pollen-grains;  plant-hairs;  fragments  of  vegetable  fibres  and 
tissue;  fibres  of  cotton,  wool,  silk,  hemp,  etc.;  starch- 
grains,  etc. 

For  the  description  of  all  these  miscellanous  organisms  and 
objects  the  reader  is  referred  to  more  comprehensive  books 
on  zoology,  botany,  and  general  microscopy. 


APPENDIX  A. 

COLLECTION    OF   SAMPLES. 

IT  cannot  be  too  strongly  emphasized  that  samples  of 
water  for  analysis  must  be  collected  with  great  care.  When- 
ever possible  the  analyst  himself  should  supervise  the  collec- 
tion. If  he  attempts  to  draw  inferences  from  analyses  of 
samples  of  water  about  the  collection  of  which  he  knows 
nothing  he  does  so  at  the  risk  of  his  reputation. 

The  quantity  of  water  required  for  a  microscopical  exami- 
nation depends  upon  the  nature  of  the  water.  Usually  one 
quart  is  sufficient,  but  a  gallon  is  to  be  preferred  and  this 
amount  is  necessary  when  a  chemical  analysis  also  is  to  be 
made.  Glass-stoppered  bottles  should  be  used,  and  they 
should  be  scrupulously  clean.  When  sent  by  express  they 
should  be  packed  in  covered  boxes  that  have  compartments 
lined  with  suitable  packing-paper  to  prevent  breaking.  In  win- 
ter it  may  be  necessary  to  use  a  felt  lining  to  prevent  freezing. 

If  collecting  a  sample  of  water  from  a  service-tap,  allow 
the  water  to  run  for  several  minutes  before  filling  the  bottle. 
Rinse  the  bottle  several  times  before  the  final  filling.  Do 
not  fill  the  bottle  completely,  but  leave  a  small  air-space.  If 
collecting  a  sample  from  a  stream  use  care  not  to  stir  up  the 
deposit  on  the  bottom,  and  do  not  allow  floating  masses  of 
vegetable  matter  to  enter  the  bottle.  This  may  be  sometimes 
prevented  by  pointing  the  mouth  of  the  bottle  down  stream. 
If  collecting  a  sample  from  a  pond  use  judgment  in  securing  a 

269 


270 


APPENDIX  A. 


representative  sample.  Do  not  fill  the  bottle  in  such  a  way 
that  the  surface-scum  may  enter.  When  collecting  samples 
from  streams  or  lakes  note  carefully  the  nature  of  the  littoral 
growths  in  the  vicinity.  These  are  sometimes  of  value  in 
the  interpretation  of  an  analysis. 

Numerous  methods  have  been  suggested  for  collecting 
samples  from  depths  below  the  surface.  The  simplest  method 
consists  of  lowering  a  weighted  stoppered  bottle  to  the  desired 
depth  and  pulling  out  the  stopper  by  means  of  a  separate 
cord.  When  the  bottle  is  full  it  may  be  drawn  to  the  surface 
with  little  probability  that  the  water  will  be  displaced.  An 
extra  precaution  to  avoid  admixture  with  the  upper  layers  of 
water  may  be  taken  by  using  a  rubber  stopper  fitted  with  a 
glass  tube  bent  at  right  angles  above  the  stopper  and  sealed 
at  the  end.  With  this  arrangement  the  water  is  allowed  to 

enter  the  bottle  by  breaking  the 
glass  tube  by  a  pull  from  an  auxili- 
ary cord.  Or  an  inflated  rubber 
ball  may  be  put  into  the  bottle. 
When  the  water  enters,  the  ball  will 
be  forced  up  into  the  neck  of  the 
bottle  on  the  inside  and  make  an 
effective  seal. 

When  collecting  samples  from 
depths  greater  than  50  ft.  it  is 
desirable  to  avoid  the  use  of  the 
auxiliary  cord.  The  following  ap- 
paratus has  proved  very  satisfactory 
down  to  depths  of  400  ft.  (See 
Fig.  23.) 

The  frame  for  holding  the  bottle 
consists  of  a  brass  wire,  A,  attached  to  a  weight,  B,  which  is 


APPARATUS  FOR 

COLLECTING  SAMPLES 
OF  WATER 


COLLECTION   OF  SAMPLES. 

made  by  rolling  a  sheet  of  brass  so  as  to  form  the  sides  of  a 
shallow  pan  and  filling  this  with  melted  lead  to  the  height  in- 
dicated by  the  dotted  line.  At  each  side  where  the  wire  rod 
is  attached  a  strip  of  brass  extends  upward,  terminating  in  a 
clip,  C.  These  brass  strips  have  considerable  spring  and  are- 
designed  to  hold  the  bottle  in  place,  as  shown  in  the  cut. 
Guides,  D,  prevent  the  strips  from  being  bent  too  far  inward, 
and  the  uprights,  A,  prevent  them  from  being  bent  too  far 
outward.  The  bottle  may  be  inserted  easily  by  holding 
back  the  springs,  C,  and  pushing  it  between  the  clips.  The 
frame  is  supported  by  the  spring,  F,  joined  to  the  sinking- 
rope,  E.  A  flexible  cord,  G,  extends  from  the  top  of  the 
spring,  E,  to  the  stopper,  //",  of  the  bottle,  /.  The  length  of 
this  cord  and  the  length  and  stiffness  of  the  spring  are  so 
adjusted  that  when  the  apparatus  is  suspended  in  the  water 
by  the  sinking-rope  the  cord  will  be  just  a  little  slack.  In 
this  condition  it  is  lowered  to  the  depth  at  which  one  wishes 
to  fill  the  bottle.  A  sudden  jerk  given  to  the  rope  stretches 
the  spring  and  produces  sufficient  tension  on  the  cord,  G,  to 
pull  out  the  stopper.  As  a  precaution  against  a  possible  loss 
of  the  apparatus  through  breaking  of,the  spring,  a  safety-cord, 
not  shown  in  the  figure,  extends  through  the  helix  connecting 
the  sinking-rope,  E,  directly  to  the  frame,  J.  This  safety- 
cord,  which  is  always  somewhat  slack,  is  also  adjusted  to 
prevent  too  great  a  stretching  of  the  spring. 

With  great  depths  it  is  necessary  to  reduce  the  size  of  the 
aperture  through  which  the  water  enters  the  bottle  and  to 
close  this  with  a  suitable  valve.  This  may  be  done  by  pass 
ing  a  piece  of  brass  tube  through  a  rubber  stopper  and  closing 
this  tube  at  the  top  with  a  brass  plug  ground  to  fit.  Or  the 
spring  may  be  us.ed  to  break  the  end  of  a  sealed  glass  tube 
inserted  in  the  stopper. 


3 

APPENDIX  B. 

TABLES   AND    FORMULA. 

WEIGHTS   AND    MEASURES— CONVERSION   TABLES. 

I  Ib.  Avoir.  =  1.215  lbs.  Troy  or  Apoth.  =  7000  grains  Troy  =  453.6  grams. 

i  Ib.  Troy  or  Apoth.  =  .823  Ib.  Avoir.  =  5760  grains  Troy  =  373.2  grams. 

i  oz.  Avoir.   —  .960  fluid  ounce  =  28.35  grams. 

I  oz.  Troy  or  Apoth.  =  1.053  fluid  ounces  =  31.10  grams. 

i  grain  Troy  =  .0648  gram. 

i  kilogram  =  2.205  lbs.  Avoir.  =  2.679  lbs-  Troy  or  Apoth. 

i  gram  =  .035  oz.  Avoir.  =  .032  oz.  Troy  or  Apoth.  =  15.432  grains  Troy. 

I  milligram  =  .0154  grain  Troy. 

i    Imperial   gallon  =  1.201    U.    S.   fluid    gallons  =  277.4    cubic    inches  = 
4546  cubic  centimeters. 

I  U.  S.   fluid    gallon  =  .833    Imperial    gallon  =  231  cubic    inches  =  3785 
cubic  centimeters. 

I  U.  S.  fluid  gallon  =  8.332  lbs.  Avoir.  =  10.127  lbs.  Troy  or  Apoth. 

i  fluid  ounce  =  1.042  oz.  Avoir.  =  .949  oz.  Troy  or  Apoth.  =  29.57  cubic  cen- 
timeters. 

I  liter  =  .264  U.  S.  fluid  gallon=.22O  Imperial  gallon  =  2i.O28  cubic  inches. 

I  liter  =  33.82  fluid  ounces  =  2.205  lbs.  Avoir.  =  2.679  lbs.  Troy  or  Apoth. 

i  cubic  centimeter  =  .033  fluid  ounce  =  .035  oz.  Avoir.  =  .032  oz.  Troy  or 
Apoth. 

i  inch  =  2.54  centimeters  =  25.4  millimeters. 

I  foot  =  30.48  centimeters. 

I  yard  =  91.44  centimeters  =  .9144  meter. 

i  meter  =  1.0936  yards  =  3.28  feet  =  39.37  inches. 

i  centimeter  =  .3937  inch. 

i  millimeter  =  .0394  inch  =  .442  Paris  lines. 

I  micron  (/*)=. oo i  millimeter=¥^¥7  inch  =  . 000039  inch  =  .ooo4  Paris  line. 

I  Paris  line  =  .089  inch  =  2.26  millimeters  =  2260.6  microns. 

i  cubic  yard  =  .7645  cubic  meter. 

i  cubic  foot  =  .O283  cubic  meter— 7.481  U.  S.  gallons=6.232  Imperial  gallons. 

i  cubic  inch  =  16.39  cubic  centimeters. 

i  cubic  meter  =  35.216  cubic  feet  =  1.308  cubic  yards. 

I  cubic  centimeter  =  .061  cubic  inch. 

272 


LABORATORY   TABLES  AND    FORMULAE. 


2/3 


TABLE    FOR    TRANSFORMING    MICROMILLIMETERS 
(MICRONS)    TO    INCHES. 


Microns. 

Decimals  of 
an  Inch. 

Fractions  of 
an  Inch. 

Microns. 

Decimals  of 
an  Inch. 

Fractions  of 
an  Inch. 

I 

.000039 

1/25000 

25 

.  000984 

I/IOOO 

2 

.000079 

I/I2500 

30 

-OOIl8l 

1/833 

3 

.000118 

1/3333 

35 

.001378 

I/7I4 

4 

.000157 

1/6250 

40 

-001575 

1/625 

5 

.000197 

1/5000 

45 

.001772 

1/533 

6 

.000236 

1/4333 

50 

.001969 

1/500 

7 

.000276 

1/3285 

60 

.002362 

1/416 

8 

.000315 

1/3125 

70 

.002756 

1/357 

9 

.000354 

1/2777 

80 

.003150 

1/312 

10 

.000394 

1/2500 

90 

•003543 

1/277 

15 

.000591 

1/1666 

IOO 

.003937 

1/250 

20 

.000787 

1/1250 

TABLE   FOR   TRANSFORMING   CENTIGRADE   TO    FAHRENHEIT 
DEGREES    OF   TEMPERATURE. 


Centigrade. 

Fahrenheit. 

Centigrade. 

Fahrenheit. 

Centigrade. 

Fahrenheit. 

-  17-7 

0 

4.0 

39-2 

23.8 

75-0 

-  15-0 

5-0 

4.4 

40.0 

25.0 

77.0 

—  12.2 

IO.O 

5-0 

41.0 

26.6 

80.0 

—  IO.O 

14.0 

7.2 

45-0 

29.4 

85.0 

~    9-4 

15.0 

IO.O 

50.0 

30.0 

86.0 

-    6.6 

20.0 

12.7 

55-0 

32.2 

90.0 

-    5-0 

23.0 

15-0 

59«o 

35.0 

95.o 

-    3-8 

25-0 

15.5 

60.0 

37-7 

IOO.O 

—    i.i 

3O.O 

18.3 

65.0 

40.0 

104.0 

0 

32.0 

20.0 

68.0 

1.6 

35-0 

21-  1 

70.0 

TABLE     FOR     TRANSFORMING     STATEMENTS     OF     CHEMICAL 

COMPOSITION. 


Grains  per 

Grains  per 

Parts  per 

Parts  per 

U.  S.  Gallon. 

Imp.  Gallon. 

100,000. 

1,000,000. 

I  grain  per 
I  grain  per 

U.  S.  gallon  
Imperial  gallon. 

I. 
0.830 

1.  2O 
I. 

I.7I 
1-43 

I7.I 
14.3 

I  part  per  I 

00,000  

0.585 

0.70 

IO.O 

I  part  per  I 

ooo  ooo  

o  058 

o  07 

o.  10 

j 

2/4 


APPENDIX  B. 


TABLE*  FOR  TRANSFORMING  COLOR  -  READINGS  OF  THE 
NESSLER  (NATURAL  WATER)  SCALE  TO  THOSE  OF  THE 
PLATINUM-COBALT  SCALE. 


Nessler 
Scale. 

Platinum- 
cobalt  Scale. 

Nessler 
Scale. 

Platinum- 
cobalt  Scale. 

Nessler 
Scale. 

Platinum- 
cobalt  Scale. 

O 

O 

•70 

-58 

.42 

.  IO 

.06 

.  IO 

•74 

.60 

•50 

.16 

.  10 

.18 

.80 

•63 

•56 

.20 

•13 

.20 

.90 

.70 

.60 

.22 

.20 

.26 

•99 

.80 

.70 

.29, 

.26 

•30 

.00 

.81 

.72 

•30 

•30 

•33 

.  IO 

.88 

.80 

.36 

.40 

•39 

•  13 

.90 

.86 

.40 

.42 

.40 

.20 

•95 

.90 

•43 

•50 

.46 

.27 

I.OO 

2.00 

•50 

•57 

•50 

•  30 

1.02 

.60 

•  52 

.40 

I.O9 

*  Based  upon  several  series  of  comparisons  by  the  analysts  of  the  Boston  Water  Supply 
Department. 

DIRECTIONS   FOR    CLEANING    GLASSWARE. 

To  clean  bottles  to  be  used  for  collecting  samples  of  water. — 
Wash  with  chromic  acid  prepared  by  saturating  strong  sul- 
phuric acid  with  potassium  bichromate.  Rinse  thoroughly 
several  times  with  distilled  water.  Drain  and  dry.  To 
remove  the  gelatinous  film  that  sometimes  collects,  use  shot, 
clean  gravel,  or  cotton  waste  and  sand,  and  afterwards  wash 
with  acid. 

To  clean  cover-slips. — Immerse  for  a  few  hours,  or  boil,  in 
nitric  acid,  or  in  chromic  acid  prepared  as  above.  Rinse  in 
water,  and  store  in  alcohol  to  which  a  little  ammonia  has  been 
added. 

To  clean  counting-cells. — Wash  with  cold  distilled  water 
and  wipe  dry  with  a  clean  linen  cloth  free  from  lint.  By 
blowing  a  stream  of  water  from  a  wash-bottle  into  the  corners 
of  the  cell  the  organisms  may  be  prevented  from  becoming 
lodged  there. 


LABORATORY    TABLES   AND   FORMULA.  275 

PRESERVATION    OF    MICROSCOPIC    ORGANISMS. 

The  microscopic  organisms  may  be  preserved  in  permanent 
mounts  upon  glass  slips  according  to  methods  described  in 
the  various  text-books  on  microscopical  technique.  For 
practical  study  it  is  more  convenient  to  preserve  them  in 
mass  in  2-oz.  bottles.  For  this  purpose  the  following  killing 
and  preservative  fluids  may  be  found  useful: 

Kings  Fluid  (for  preserving  algae,  etc.). — 

Camphor-water* 50  grams. 

Distilled  water 50        ' ' 

Glacial  acetic  acid. 0.50*' 

Copper  nitrate,  crystals 0.20  '  * 

Copper  chloride,  crystals 0.20  " 

Corrosive  Acetic  Acid  (for  killing). — Saturated  solution  of 
mercuric  chloride  plus  10$  of  acetic  acid.  After  using,  wash 
with  water.  Preserve  in  alcohol. 

Formaldehyde. — For  killing,  use  a  40$  solution,  sold  under 
the  name  of  "Formalin."  For  preserving,  use  solutions  vary- 
ing from  5$  to  10$,  according  to  the  organisms. 

Picro-sulphuric  Acid  ([or  killing). — 

Distilled  water  saturated  with  picric  acid.. . .    100  c.c. 
Sulphuric  acid,  strong.. 2  c.c. 

After  using,  wash  with  60%  alcohol. 

Corrosive  Sublimate  (for  killing  Protozoa). — To  water  con- 
taining the  organisms  add  an  equal  volume  of  saturated  cor- 
rosive sublimate.  Decant,  and  add  50$  alcohol,  changing  this 
in  an  hour  to  70$. 

*  Made  by  letting  a  lump  of  camphor  stand  in  distilled  water  for  a  few 
days. 


APPENDIX  C. 

BIBLIOGRAPHY. 

THE  following  is  a  partial  list  of  references  to  articles  on  the 
microscopic  organisms  and  their  relation  to  drinking-water,  to- 
gether with  such  other  references  as  will  enable  the  student  *o 
investigate  the  broader  subjects  of  sanitary  water-analysis  and 
limnology. 

MICROSCOPY. 

Bausch,  Edw.    Manipulation  of  the  Microscope.    Rochester,  N.  Y. :  Bausch  & 

Lomb  Optical  Co. 
Beale,  L.  S.     How  to  Work  with  the  Microscope.    5th  edition.    Philadelphia: 

Lindsay   &  Blakiston,  1880. 
Behrens,  J.  W.    A  Guide  for  the  Microscopical   Investigation  of  Vegetable 

Substances.     Translated  by  Rev.  A.  B.  Hervey.     Boston:  S.  E.  Cassino, 

1885. 
Carpenter,  W.  B.      The    Microscope    and    its    Revelations,      yth    edition. 

Edited  by  Dallinger.     Philadelphia:   P.  Blakiston,  Son  &  Co.,  1891. 
Davis,  Geo.  E.     Practical   Microscopy.      3d   edition.      Philadelphia:   J.    B. 

Lippincott  Co.,  1889. 
Davis  and  Mathews.     The  Preparation  and  Mounting  of  Microscopic  Objects. 

New  York:  G.  P.  Putnam's  Sons,  1890. 
Deby,  Julian.     A  Bibliography  of  the  Microscope  and  Micrographic  Studies. 

London:  D.  Bogue,  1882. 
Frey,   H.    The   Microscope   and  Microscopical  Technology.     New   York: 

Wm.  Wood    &  Co.,  1880. 
•Gage,  S.    H.     The  Microscope  and  Microscopical  Methods.      7th   edition 

Ithaca,  N.  Y.:    Comstock  Pub.  Co. 

276 


BIBLIOGRAPHY. 

Lankester,  E.     Half -hours  with  the  Microscope:    A  Popular  Guide  to  the 

Use  of  the  Microscope  as  a  Means  of  Amusement  and  Instruction. 

20th  edition.     London,   1898. 
Naegeli    and  Schwendener.     The  Microscope  in  Theory  and  Practice.   2d 

edition.     London:    Swan,  Sonnenschein,  Lowry    &  Co. 
Nave,  J.     Collector's  Handy-book.     London:  W.  H.  Allen  &  Co. 
Pringle,     Andrew.     Practical     Photo-micrography.     New     York:      Scovell 

&  Adams  Co.,   1890. 
Van  Heurck,  H.     Le  Microscope — sa  construction,  son  mainiement,  et  son 

application  speciale  a  1'anatomie  vegetale  et  aux  diatomees.     3d  edition. 

Brussels,  1878. 

BIOLOGY,  BOTANY,  ZOOLOGY. 

Bessey,  C.   F.     Botany   (Advanced  Course).     New  York:    Henry  Holt    & 

Co.,  1888. 
Davenport,  Chas.  B.     Experimental  Morphology.    Part  I.  Effect  of  Chemical 

and  Physical  Agents  upon  Protoplasm.     Part  II.  Effect  of  Chemical 

and  Physical  Agents  upon  Growth.     New  York:  Macmillan    Co. 
Dragendorff,  G.     Plant  Analysis,  Qualitative  and  Quantitative. 
Goebel,  K.     Outlines  of  Classification  and  Special  Morphology  of  Plants. 
Huxley    and    Martin.      A    Course   of   Elementary   Instruction   in    Practical 

Biology.     London:    Macmillan   &  Co.,  1883. 
Klebs,  G.      Die  Bedingungen  d.  Fortpflanzung  bei  einigen  Algen  u.  Pilzen. 

Jena:    Gustav  Fischer,  1896. 
Mandel,   John   A.     Hand-book   for   Eio-chemical  Laboratory.     New  York: 

John  Wiley   &  Sons,  1896. 
Parker,  T.  Jeffrey,  and  Haswell,  W.  A.     A  Text-book  of  Zoology.     London: 

Macmillan   &  Co.,  1897. 
Poulsen,  V.  A.     Botanical  Micro-chemistry.     Translated  by  Wm.  Trelease. 

Boston:   Cassino   &  Co.,  1884. 

Ranvier.     Traite  d'Histologie.     Paris:    Savy,  1875,  1882. 
Sachs,  Julius.     Text-book  of  Botany.     Oxford:    Clarendon  Press,  1882. 
Schafer.     Essentials  of  Histology.     Philadelphia:    Lea,  1885. 
Sedgwick,    Wm.    T.,    and    E.    B.    Wilson.      General    Biology.     New   York: 

Henry  Holt  &  Co.,  1895. 
Stohr.     Text -book    of    Histology.     Translation    by    Schafer.     Philadelphia: 

Blakiston,  1896. 
Strasburger,    E.     Microscopic    Botany:     A   Manual   of    the   Microscope   in 

Vegetable  Histology.     Boston:    S.  E.  Cassino,  1887. 

Taylor,  J.   E.      The  Aquarium:    Its  Inhabitants,  Structure,  and  Manage- 
ment.    London:   W.  H.  Allen   &  Co.,  1884. 


278  APPENDIX   C. 

Thomson,  J.  A.     The  Study  of  Animal  Life.     University  Extension  Manuals. 

New  York,  1892. 
Vines.     Students'    Text-book    of    Botany.     London:     Sonnenschein,    1894, 

1895. 
Warming.     Text-book  of  Botany.     Translation  by  M.  C.  Potter.     London: 

Sonnenschein,  1895. 
Zimmermann,     A.     Die     botanische     Mikrotechnik.     Ein     Handbuch     der 

mikroskopischen    Preparations-,    Reactions-,    und    Tinctionsmethoden. 

Tubingen,  1892. 


MICROSCOPICAL  EXAMINATION  OF  WATER. 

Bell,  James.     Microscopical  Examination  of  Water  for  Domestic  Use.     Mo. 

Micro.  Jour.,  V,  163.     London,  1871. 
Calkins,   Gary   N.      The   Microscopical   Examination   of  Water.      23d  An. 

Rep.  Mass.  St.  Bd.  of  Health,  1891. 

Certes,  A.     Analyse  Micrographique  des  Eaux.     Paris:  B.  Tignol,  1883. 
Drown,   Thomas  M.      The  Analysis'    of  Water:     Chemical,   Microscopical, 

arid  Bacteriological.     Jour.  N.  E.  Water  Works  Assoc.,  Dec.,  1889. 
Hansen,  S.  Ch.      Methode  zur  Analyse  des  Brauwassers  in  Riicksicht  auf 

Mikroorganismen.     Centb.  f.  Bacter.  et  Parasitenk.,  Ill,   1888. 
Harz,    C.    0.      Mikroskopische     Untersuchung    des    Brunnetiwajssers    fur 

hygienische  Zwecke.     Zeitschrift  f.  Biologic,  XII,  100,  1876. 
Hassall,  A.  H.     A  Microscopic  Examination  of  the  Water  Supplied  to  the 

Inhabitants  of  London  and  the  Suburban  Districts.     London,  1850. 

—  Food:    Its  Adulterations  and  the  Methods  for  their  Detection.     Lon- 
don:  Longmans,  Green  &  Co.,  1876. 
Hirt,   L.     Ueber   den   Principien    und   die   Methode   der   Mikroskopischen 

Untersuchung  des  Wassers.     Zeitschrift  fur  Biologic,    1879. 
Hitchcock,   R.     The   Biological   Examination   of   Water.     Am.    Mo.    Micr. 

Jour.,  VIII,  9,  1887. 
Hovenden,  F.     Examining  Thin  Films  of  Water.     i8th  An.  Rept.  London 

Micro,  and  Nat.  Hist.  Club,  1889,  10. 
Hulwa,  Franz.     Beitrage  zur  Schwemmkanalization  und  Wasser-Versorgung 

der    Stadt    Breslau.     Centralblatt    fur    allgemeine    Gesundheitspflege, 

Erganzungsheft,  I,  89.     Bronn,  1885. 
Jackson,  D.  D.     On  an  Improvement  in  the  Sedgwick -Rafter  Method  for 

the  Microscopical  Examination  of  Drinking  Water.     Tech,  Quarterly, 

IX,  Dec.,  1896. 
Jackson,  D.   D.      An   Improved  Filter  for  Microscopical  Water  Analysis. 

Tech.  Quarterly,  XI,  Dec.,  1898. 


BIBLIOGRAPHY.  2/9 

Jolles,  M.     Die  bacteriologische  und  mikroskopische  Wasseruntersuchung 

Wien,  1892. 
Kean,  A.  L.      A  New  Method  for  the  Microscopical  Examination  of  Water. 

Science,  Feb.  15,  1889;   Eng.  News,  March  30,  1889. 
Leeds,  A.  R.      Quantitative  Estimation  of  Micro-Organisms.     The  Stevens 

Indicator,  XIV,  Jan.,  1897. 

MacDonald,  J.  D.      A   Guide  to  the  Microscopical  Examination  of  Drink- 
ing Water.     26.  edition.     London:    J.    &  A.  Churchill,  1883. 
Mez,     Carl.      Mikroskopische     Wasseranalyse.     Berlin:      Julius     Springer, 

1898. 
Moore,  Geo.  T.     Methods  for  Growing  Pure  Cultures  in  Algae.     Journal  of 

Applied  Microscopy  and  Laboratory  Methods.     Vol.  VI,  No.  5. 
Neuvelle.     Des  Eaux  de  Paris:   Essai  d'analyse  micrographique  comparee. 

Paris,  1880. 
Radlkofer,  L.     Mikroskopische  Untersuchung  der    organischen  Substanzen 

im  Brunnenwasser.     Zeitschrift  fur  Biologic,  1865. 
Rafter,  George  W.     On  the  Use  of  the  Microscope  in  Determining  the  Sanitary 

Value  of  Potable   Water,  with  Special  Reference  to  the  Study  of  the 

Biology  of  the  Water  of  Hemlock  Lake.     Proc.  Micro.  Sect.  Rochester 

Acad.  of  Sciences,  1886. 
= —  How  to  Study  the  Biology  of  a  Water  Supply.     A  paper  read  before 

the  Section  of  Microscopy,  Rochester  Acad.  of  Sciences. 
-  The   Biological   Examination  of  Potable  \Vate'r.      Proc.   Rochester 

Acad.  Sciences,  I,  33-44.     Rochester,  1890. 
—  On  Some  Recent  Advances   in  Water  Analysis  and  the  Use  of  the 

Microscope  for  the  Detection  of  Sewage  Contamination.    Am.  Month. 

Micro.  Jour.,  May,   1893. 

The    Microscopical    Examination    of    Potable    Water.     No.    103    in 


Van  Nostrand  Science  Series. 
Sedgwick,    William    T.      Biological    Examination    of    Water,    Technology 

Quarterly,  II,  67. 

-  Biological  Water  Analysis.     Proc.  Soc.  Arts,  1888-89. 

—  Recent    Progress   in   Biological   Water   Analysis.     Jour.    N.    E.    W 

W.  Assoc.,  IV,  Sept.,  1889. 

Sorby,  H.   C.      Microscopical  Examination  of  Water  for  Organic  Impuri- 
ties.    Jour.  Roy.  Micro.  ScL,  Series  2,  IV,  1884. 

—  Detection  of  Sewage  Contamination  by  the  Use  of  the  Microscope 

and  on  the  Purifying  Action  of  Minute  Animals  and  Plants.      Jour. 

Soc.  Arts,  XXXII,  929,  1884;  Jour.  Roy.  Micr.  Soc.,  Series  2,  IV,  988, 

1884. 
Tate,  A.  N.     Microscopical  Examination  of  Potable  Water.      Engl.  Mechanic, 

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280  APPENDIX   C. 

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Garrett,  J.  H.  The  Spontaneous  Pollution  of  Reservoirs.  (Odor  pro- 
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Hassall,  Arthur  H.  The  Diatomaceae  in  the  Water  Supplied  to  the  In- 
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Hill,  W.  R.     The  Method  of  Removing  Organisms  from  the  Water  in  the 

Distributing  Reservoir  of  the  City  of  Syracuse.     N.  Y.  Jour,  of  N.  E. 

Water  Works  Asso.,  Vol.  XIV,  No.  3. 
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Two  Growths  of  Chlamydomonas   in  Connecticut.     Trans.   Amer- 

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On  Removing  Organisms  from  Water.     Jour,  of  the  New  England 


Water  Works  Assoc.,  Vol.  XIV,  No.  3. 
Horsford,  E.  N.,  and  Chas.  T.  Jackson.      Report  on  the  Disagreeable  Tastes 

and  Odors  in  the  Cochituate  Water  Supply.     Ann.  Rept.  Coch.  Water 

Bd.,  1854. 
Hyatt,  J.  D.     Sporadic  Growth  of  Certain  Diatoms  and  the  Relation  thereof 

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Hueppe,    F.     Die    hygienische    Beurtheilung   des    Trinkwassers   vom    bio- 

logischen   Standpunkte.      Schilling's  Journal  fur  Gasbeleuchtung  und 

Wasserversorgung.     1887. 
Index   Catalogue    of  the   Library  of  the   Surgeon-General's  Office,  U.  S.  A. 

Washington,    1895.     Vol.   XVI   contains  an  extensive  bibliography  of 

Water  and  Water  Supply.        Continued  in  the  Index  Medicus. 
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Kean,  A.  L.,  and  E.  0.  Jordan.  A  Glass  of  Water.  A  brief  description 
of  the  organisms  in  Boston  tap  water.  Technology  Quarterly,  Feb.,  1889. 

Kellicott,  S.  D.  Notes  on  Microscopic  Life  in  the  Buffalo  Water  Supply. 
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Konig,  Dr.  J.,  and  Emmerich,  Prof.  Dr.  R.  Die  Bedeutung  der  Chemischen 
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Lattimore,  S.  A.  Report  on  the  Recent  Peculiar  Condition  of  the  Hem- 
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Le  Conte,  L.  J.  Some  Facts  and  Conclusions  bearing  upon  the  Relations 
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Leeds,  Albert  R.  Report  on  the  Results  of  the  Chemical  and  Microscop- 
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Final  Report  of  a  Chemical  Investigation  of  the  Water  Supply  of 

Philadelphia.     Ann.  Rept.   Chief  Eng.,   1885,  379-400. 

Report  of  the  Committee  on  Animal  and  Vegetable  Growths  affect- 


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1902. 
Mass.  State  Board  of  Health.     Special  Reports. 

1890.     Special  Report  on  Examination  of  Water  Supplies. 

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298  APPENDIX   C. 

Mass.  State  Board  of  Health.     Special  Reports— (Continued.) 

Report  upon  the  Organisms,  except  the  Bacteria,  found  in  the  Waters 
of  the  State.  G.  H.  Parker. 

Summary  of  Water-Supply  Statistics — Rainfall,  Flow  of  Streams,  Tem- 
perature of  Air  and  Water.  F.  P.  Stearns. 

A  Classification  of  the  Drinking  Waters  of  the  State. 

Special  Topics  relating  to  the  Quality  of  Public  Water  Supplies— The 
Effect  of  Storage,  Investigation  of  Deep  Ponds,  Special  Character- 
istics of  Cert  in  Surface  Waters,  The  Natural  Filtration  of  Water. 
F.  P.  Stearns  and  T.  M.  Drown. 

The  Pollution  and  Self-Purification  of  Streams.     F.  P.  Stearns. 
1890.     Special  Report  on  Purification  of  Sewage  and  Water. 

Filtration  of  Sewage  and  Water,  and  Chemical  Precipitation  of  Sewage. 
Hiram  F.  Mills. 

A  Report  of  the  Chemical  Work  of  the  Lawrence  Experiment  Station. 
T.  M.  Drown  and  Allen  Hazen. 

Experiments  upon  the  Chemical  Precipitation  of  Sewage  at  the  Lawrence 
Experiment  Station.  Allen  Hazen. 

A  Report  of  the  Biological  Work  of  the  Lawrence  Experiment  Station. 
Wm.  T.  Sedgwick. 

Investigations  upon  Nitrification  and  the  Nitrifying  Organism.     E.  O. 

Jordan  and  Ellen  H.  Richards. 
1895.     Special   Report  upon  a  Metropolitan  Water  Supply  for  Boston. 

Improvement  of  the  Quality  of  the  Sudbury  River  Water  by  the  Drainage 
of  the  Swamps  upon  the  Watershed.  Desmond  FitzGerald. 

On  the  Amount  and  Character  of  Organic  Matter  in  Soils  and  its  Bearing 

on  the  Storing  of  Water  in  Reservoirs.     T.  M.  Drown. 
Mass.  State  Board  of  Health.     Annual  Reports. 

The  annual  reports  since  1890  contain  reports  upon  the  examination 
of  water  supplies  and  experiments  on  the  filtration  of  sewage  and 
water,  besides  the  following  papers: 

1890.  Suggestion    as    to    the    Selection    of    Sources    of    Water    Supply. 

By  F.  P.  Stearns. 

1891.  On  the  Amount  of  Dissolved  Oxygen  contained  in  Waters  of  Ponds 

and  Reservoirs  at  Different  Depths.     T.  M.  Drown. 
The  Effect  of  Aeration  of  Natural  Waters.     T.  M.  Drown. 
The  Microscopical  Examination  of  Water.     Gary  N.  Calkins. 
The  Differentiation  of  the  Bacillus  of  Typhoid  Fever.     G.  W.  Fuller. 

1891.  On  Uroglena.    Gary  N.  Calkins. 

1892.  Interpretation  of  Water  Analyses.     T.  M.  Drown. 

On  the  Amount  of  Dissolved  Oxygen  in  the  Water  of  Ponds  and  Reser- 
voirs at  Different  Depths  in  Winter,  under  the  Ice.  T.  M.  Drown. 


BIBLIOGRAPHY.  299 

Mass.  State  Board  of  Health.     Annual  Reports — (Continued). 

On  the  Mineral  Contents  of  Some  Natural  Waters  in  Massachusetts. 

T.  M.  Drown. 
A  Study  of  odors  observed  in  the  Drinking  Waters  of  Massachusetts. 

Gary  N.  Calkins. 
Seasonal   Distribution   of  Microscopic   Organisms   in   Surface   Waters. 

Gary  N.  Calkins. 
Some  Physical  Properties  of  Sands  and  Gravels  with  Special  Reference 

to  their  Use  in  Filtration.     Allen  Hazen. 
Reports  on   Epidemics  of  Typhoid  Fever  in  Massachusetts  in   1892. 

Wm.  T.  Sedgwick. 

1893.  On  the  Amount  and  Character  of  Organic  Matter  in  Soils,  and  its 
Bearing  on  the  Storage   of   Water  in   Reservoirs.      T.  M.  Drown. 

The  Filter  of  the  Water  Supply  of  the  City  of  Lawrence  and  its  Results. 
Hiram  F.  Mills. 

1894.  The  Composition  of  the  Water  of  Deep  Wells.     T.  M.  Drown. 
The  Bacterial  Contents  of  Certain  Ground  Waters.     W.  T.  Sedgwick. 
Physical  and  Chemical  Properties  of  Sand.     H.  W.  Clark. 

Report  upon  an  Epidemic  of  Typhoid  Fever  in  Marlborough.     Wm. 
T.  Sedgwick . 

1895.  The  Hardness  of  Water  and  Methods  by  which  it  is  Determined. 

Ellen  H.  Richards. 

Methods   Employed   for   the    Quantitative   Determination   of   Bacteria 
in  Sewage  and  Water.     G.  W.  Fuller  and  W.  R.  Copeland. 

1896.  No  special  papers  on  water  or  sewage  analysis. 

1897.  No  special  papers  on  water  or  sewage  ana'ysis. 

1898.  An  Investigation  of  the  Action  of  Water  upon  Lead,  Tin  and  Zinc. 
H.  W.  Clark. 

The  Purification  of  the  Sewage  of  Cities  and  Towns  in  Massachusetts. 
X.  H.  Goodnough  and  W.  S.  Johnson. 

1899.  The  Occurrence  of  Iron  in  Ground  Waters.     H.  W.  Clark. 

1900.  The  Action  of  Water  upon  Metallic  or  Metal  Lined  Surface  Pipes. 
H.  W.  Clark  and  F.  B.  Forbes. 

An  Investigation  in  regard  to  the  Retention  of  Bacteria  in  Ice.     H.  W. 

Clark. 
Studies  of  the  Efficiency  of  Water  Filters  in  removing  different  species 

of  Bacteria.     S.  DeM.  Gage. 

1901.  Experimental   Filtration   of  the    Water   Supply   of  Springfield,  at 
Ludlow. 

A  Study   of  the  Stability  of  the  Effluents  of  Sewage  Filters  of  Coarse 
Materials.    H.  W.  Clark. 


300  APPENDIX   C. 

Mass.  State  Board  of  Health.     Annual  Reports — Continued. 

Bacteriological  Studies  at  the  Lawrence  Experiment  Station,  with  special 
reference  to  the  Determination  of  B.  coli.     S.  DeM.  Gage. 

1902.  On  the  Value  of  Tests  for  Bacteria  of  Specific  Types  as  an  Index  of 
Pollution.     H.  W.  Clark  and  S.  DeM.  Gage. 

Report  upon  the  Examination  of  the  Outlets  of  Sewers. 

1903.  Examination  of  Sewer  Outlets  and  the  effect  of  Sewage  Disposal. 
McElroy,  Samuel.     Organic  Life  and  Matter  in  Water.     Proc.  Am.  Water 

Works  Assoc.     nth  Annual  Meeting,  1887. 
Mills,  H.     Micro-Organisms  in  Buffalo  Water  Supply  and  in  Niagara  River. 

Proc.  Am.  Soc.  Micro.,  1882,  165-175. 
Moore,  G.  T.      Algae  as  a  Cause  of  the  Contamination  of  Drinking  Water. 

American  Journal  of  Pharmacy,  January,  1900. 
Moore,  George    T.,  and    Karl  F.  Kellerman.     A    Method  of  Destroying  or 

Preventing  the  Growth  of  Algae  and  Certain  Pathogenic  Bacteria  in 

Water  Supplies.     U.  S.  Dept.  Agriculture,  Bureau  of  Plant  Industry, 

Bulletin  No.  64.     1904. 
Copper  as  an  Algicide  and  Disinfectant  in  Water  Supplies.     Bulletin 

No.  76,  1905. 
Moriez,   R.     L'odeur  des  cours  d'eau  au  square  Vauban  a  Lille.     Rev. 

biol.  du  nord  de  la  France,  1893-4;  55-61. 
Nichols,  William  R.     Report  of  the  Examination  of  Mystic  Pond  and  its 

Sources   of   Supply.     Rept.    Mass.    State    Board   of   Health,    II,  1871, 

387-390. 
On  the  Present  Condition  of  Certain  Rivers  of  Massachusetts,  etc. 

Rept.  Mass.  State  Board  of  Health,  V  (1874),  61-152. 

—  (with  W.   G.   Farlow  and  E.   Burgess).     On  a  Peculiar  Condition 
of  the  Water  Supplied  to  the  City  of  Boston,  1875-76.     Rept.  Coch. 
Water  Board,  1876. 

Report  on  Matters  connected  with  the  Boston  Water  Supply.     Rept. 

Boston  Water  Board,  I,  1877,  11-15. 

—  Circular  of  Information  about  Certain  Fresh-water  Algae.     [Printed 
for   private   distribution.]    Also,    in    Rept.    Cambridge   Water    Board, 
1877,  8-13. 

—  On  the  Condition  of  the  Water  of  Springfield,  Mass.,  during  1876 
Rept.  of  Water  Commissioners,  Springfield,  1877. 

—  Report  on  a  Peculiar  Taste  and  Odor  of  the  New  London  (Conn.) 
Water.     Rept.  New  London  Water  Commissioners,  1880,  27-30. 

Tastes  and  Odors  of  Surface  Waters.     Jour.  Assoc.  of  Eng.  Soc., 


Jan.,  1882. 

Ohio  State    Board  of  Health.     Preliminary  Report  of  an  Investigation  of 
Rivers  and  Deep  Ground  Waters  of  Ohio.     1897-8. 


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—  Some  of  the  Minute  Animals  which  Assist  the  Self-Purification  of 
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— -  Some  of  the  Circumstances  affecting  the  Quality  of  a  Water  Supply. 

Proc.  Am.  Water  Works  Assoc.,  i2th  Ann.  Meeting,  1892. 

— -  (and   M.  L.  Mallory  and  J.  Edw.    Lane)  Volvox   globator  as   the 

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1888.     Ann.  Rept.  of  Ex.  Bd.  of  Rochester,  N.  Y.,  for  2  years  ending 

April  i,  1889. 

—  On  the  Fresh-water  Algae  and  their  Relation  to  the  Purity  of  Public 
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—  On  Lake  Eri   as  a  Water  Supply  for  the  Towns  on  its  Borders.     Buffalo 

Medical  Journal,  Aug.,    1896.      Read  before  Micro.  Club  of    Buffalo 

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Reading,  Pa.     Report  of  the  Board  of  Water  Commissioners  on  the  Puri- 
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Report  of  Allen  Hazen.     Feb.  28,  1898. 
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Spongilla.)     Boston,  1881. 
Richards,  Ellen  H.,  and  Isabel  F.  Hyams.     The  Composition  of  Oscillatoria 

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Abstract  in  Proc.  of  Am.  Soc.  Adv.  Sci.,  Aug.,  1898. 
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302  APPENDIX   C 

Scott,  W.  B.,  and  others.      Water  and  Water  Supply.     A  series  of  papers. 

International  Health  Exhibition,  1884. 
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—  Report  on  the  Biological  Work  of  the  Lawrence  Experiment  Station. 
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ton des  grossen  Plonersees,  II,  1894,  91-137.  Ueber  die  wechselnde 
Quantitat  des  Planktons  im  grossen  Plonersee,  III,  1895,  97-117.  Ueber 
die  horizontale  und  verticale  Verbreitung  limnetischer  Organismen, 
III,  1895,  128-148.  Quantitative  Untersuchungen  iiber  das  Limno- 
plankton,  IV,  1896,  1-64.  Ergebnisse  einer  bielog.  Excursion  an  die 
Hochseen  des  Riesengebirges,  IV,  1896,  65-87. 

Ein  neues  Conservierungsmittel  fur  gewisse  Flagellaten  des  Planktons. 

Zoologischer  Anzeiger,  Bd.  XXII,  No.  579,  vom  Feb.  6,  1899. 

Ueber  Pseudopodienbildung  bei  einem  Dinoflagellaten.  Biologiscbes 

Centralblatt,  Bd.  XIX,  Nr.  4,  February,  1899. 

Die  Rhizopoden  und  Heliosoen  des  Siisswasserplanktons.  Zoolo- 

gischen  Anzeiger,  Bd.  XXII,  No.  579,  vom  Feb.,  1899. 

Fauna  des  grossen  Plb'ner  Sees.  Forschungsber.  d.  biol.  Station 

zu  Plon,  II,  57-64,  1894. 


APPENDIX   D. 


GLOSSARY    TO    PART    II. 


Adoral,  relating  to  the  mouth. 

Aeruginous,  of  the  color  of  verdigris; 
blue-green. 

Alate,  winged. 

Amylaceous,  resembling  starch. 

Anal,  relating  to  the  anus. 

Annulate,  marked  with  rings. 

Antheridia,  reproductive  organs  sup- 
posed to  be  analogous  to  anthers. 

Arcuate,  bent  like  a  knee. 

Articulate,  composed  of  joints. 

Bacillar,  rod-like. 

Bifid,  two-cleft. 

Birotulate,  with  two  recurved  rounded 
ends. 

Botryoid,  clustered  like  a  bunch  of 
grapes. 

Buccal,  relating  to  the  cheek. 

Campanulate,  bell-shaped. 

Capitate,  collected  in  a  head. 

Carapace,  a  hard  shell. 

Carinate,  like  a  keel. 

Caudal,  relating  to  the  tail. 

Cervical,  relating  to  the  neck. 

Chitinous,  horny. 

Ciliated,  provided  with  cilia,  or  hair- 
like  appendages. 

Circinate,  curled  round,  coiled,  or 
spirally  rolled  up. 

Cirrose,  curled  as  a  tendril. 


Clathrate,  perforated  or  latticed  like 
a  window. 

Coccus,  a  minute  spherical  form. 

Ccenobium,  a  community  of  a  definite 
number  of  individuals  united  in 
one  body. 

Concatenate,  linked  like  a  chain. 

Connate,  united  congenitally. 

Convolute,  rolled  together. 

Cortical,  relating  to  the  external 
layers. 

Crenate,  notched  or  scalloped. 

Cuneate,  wedge-shaped. 

Cymbiform,  boat-shaped. 

Cyst,  a  membranous  sac  without 
opening. 

Dentate,  toothed. 

Denticulate,  finely  toothed. 

Dichotomous,  dividing  by  pairs  from 
top  to  bottom. 

Dioecious,  the  males  and  females 
represented  in  separate  individuals. 

Ectoderm,  the  external  of  two  ger- 
minal cellular  layers. 

Emarginate,  with  a  notch  cut  out  of 
the  margin  at  the  end. 

Encuirassed,  with  an  indurated  dorsal 
shield. 

Encysted,  enclosed  in  a  cryst  or  blad- 
der. 

3" 


3I2 


APPENDIX  D. 


Endochrome,  the  coloring  matter  of 
cells. 

Endoplast,  the  nucleus  of  a  protozoan 
cell. 

Fasciculate,  in  bundles  from  a  com- 
mon point. 

Filiform,  long,   slender,  thread-like. 

Flagellate,  provided  with  flagella,  or 
lash-like  appendages. 

Foliaceous,  resembling  a  leaf. 

Forcipitate,  like  forceps. 

Funicular,  like  a  cord  or  thread. 

Furcate,  forked  or  divergently 
branched. 

Fusiform,  tapering  like  a  spindle. 

Gibbous,  swollen,  convex. 

Gonidia,  propagativ£  bodies  of  small 
size  not  produced  by  act  of  fertili- 
zation. 

Heterocyst,  interspersed  cells  of  a 
special  character  differing  from 
their  neighbors. 

Holophytic,  like  a  plant. 

Hormogons,  special  reproductive 
bodies  composed  of  short  chains 
of  cells,  parts  of  internal  filaments. 

Hyaline,  transparent. 

Hyphae,  filaments  of  the  vegetative 
portion  of  a  fungus. 

Indurated,  hardened. 

Intercalated,  interspersed,  placed  be- 
tween others. 

Involute,  rolled  inward. 

Lamellated,  lamellose,  in  layers. 

Lanceolate,  lance-shaped,  tapering  at 
each  end. 

Lenticular,  like  a  lens. 

Lophophore,  an  organ  bearing  ten- 
tacles, found  on  the  Bryozoa. 

Lorica,  a  hard  protective  coat. 

Lunate,  crescent-shaped. 

Macrogonidia,  large  gonidia. 

Macrospores,  large  spores. 

Matrix,  the  birth  cavity. 

Microgonidia,  small  gonidia. 


Mona.vonic,  with  but  one  axis. 

Moniliform,  like  a  necklace,  con- 
tracted at  regular  intervals. 

Monoecious,  male  and  female  repre- 
sented in  one  individual. 

Mucronate,  having  a  small  tip. 

Mycelium,  the  vegetative  portion  of 
a  fungus. 

Naviculoid,  boat-shaped. 

Oosphere,  an  ovarian  sac. 

Oospore,  spore  produced  in  an 
ovarian  sac. 

Oral,  relating  to  the  mouth. 

Parietal,  growing  near  the  wall- 

Peristome,  the  oral  region. 

Pinnatifid,  shaped  like  a  feather. 

Pclythecium,  an  assemblage  of  many 
loricae. 

Punctate,  studded  with  points  or  dots. 

Pyriform,  pear-shaped. 

Reniform,  kidney-shaped. 

Replicate,  folded  back. 

Reticulate,  latticed. 

Retractile,  capable  of  being  drawn 
back. 

Saccate,  like  a  bag. 

Sarcode,  the  primary  vital  matter  of 
animal  cells  (Protoplasm). 

Scalariform,  ladder-like. 

Segregate,  set  apart  from  others. 

Septate,  separated  by  partitions. 

Setiform,  in  the  form  of  a  bristle. 

Sigmoidal,  S-shaped. 

Sinuate,  with  notches  or  depressions. 

Spermatozoids,  thread-like  bodies, 
motile,  and  possessing  fecundative 
power. 

Sporangium,  sporange,  a  spore-case. 

Sporocarp,  the  covering  or  capsule 
enclosing  a  spore. 

Sporoderm,  the  covering  of  a  spore. 

Statoblasts,  the  winter  eggs,  or  re- 
productive bodies  of  the  Bryozoa 
and  Spongidse. 

Striate,  covered  with  striae. 


GLOSSARY   TO   PART  II. 


3*3 


Styligerous,  bearing  styles  or  prom- 
inences. 

Sub-,  a  prefix  indicating  "  almost," 
or  "  nearly." 

Suborbicular,  almost  spherical. 

Thallus,  a  leaf-like  expansion. 

Trichocyst,  a  rod-like  body  developed 
in  the  cortical  layer  of  some  pro- 
tozoa. 

Trichome,  the  thread  or  filament  of 
filamentous  algae. 


Turbinate,  shaped  like  a  top. 

Utriculate,  inflated. 

Vacuolated,      containing      drops      or 

vacuoles. 

Vesiculiform,  bladder-like. 
Zoodendrum,  a  bill-like  colony-stalk. 
Zoogonidia,    gonidia    endowed    with 

motion. 

Zoospores,  locomotive  spores. 
Zygospore,    a    spore    resulting    from 

conjugation. 


INDEX. 


Absorption  of  light  by  water,  79 

Acarina,  267 

Achlya,  224 

Acineta,  247 

Acinetaria,  246 

Actinophrys,  231 

Aeration,  effect  on  algae,  153 

Algae,  204 

Amorphous  matter,  29 

Amoeba,  229 

Amphipoda,  256 

Amphora,  184 

Anabaena,  200 

,  decomposition  of,  131 

,  in  Cedar  Swamp,  135 

,  oil  isolated,  128 

Anacharis,  268 
Anguillula,  267 
Anthophysa,  233 
Anuraea,  255 
Anuraeadae,  255 
Aphamzomenon,  201 

— ,  growth  in  winter,  105 
Aphanocapsa,  197 
Aphanothece,  198 
Arcella,  229 

Aromatic  odors,  128-130 
Arthrodesmus,  214 
Asco*n\  cetes,  222 
Asellus  aquaticus,  256 
Aspergillus,  223 
Asplanchna,  253 


Asplanchnadae,  253 
Asterionella,  188 

— ,  growth  of,  in  Brooklyn,  149 

— ,  growth  of,  in  ground-water,  148 

— ,  weight  of,  133 
Attachment    to    filter    funnels,    Sedg- 

wick -Rafter  Method,  19,  20 
Autumnal      overtruning       (autumnal 

circulation),  62 


Bacteria,  in  distribution  pipes,  162 

Bacteria,  affected  by  algae,  146 

Bacteriological  examination  of 
water,  8 

Batrachospermum,  267 

Bdelloida,  252 

Beggiatoa,  193 

Blank,  for  recording  results  of  mi- 
croscopical examination,  32 

Bleaching  of  water  by  sunlight,  73 

Bosmina,  260 

Boston  Water  Works  Laboratory,  2 

Botryococcus,  207 

Brachionidae,  255 

Brachionus,  255 

Branchipus,  259 

Brooklyn  Water  Works  Laboratory,  2 

Brooklyn  water-supply,  growth  of 
Asterionella,  149 

,  growths  of  Paludicella,  169 

Bryozoa,  261 

,  growth  of,  in  water-pipes,  166 


INDEX. 


Bursaria,  244 

Canals,  organisms  found  in,  48 

Canthocamptus,  258 

Carbonic  acid,  96 

Cell,  errors  in  the,  28;    used  in  Sedg- 
wick-Rafter  Method,  21 

Centrifuge,    use   of,    in   concentrating 
microscopic  organisms,  6,  38 

Ceratium,  239 

Ceratophyllum,  267 

Cercomonadina,  233 

Cercomonas,  233 

Chaetonotus,  267 

Chaetophora,  219 

Chaetophoraceae,  218 

Chara,  219 

,  odor  caused  by,  123 

Characeae,  219 

Chemical  analysis  of  water,  8 
— ,  relation  to  the  growth  of 
microscopic  organisms,  91-97 

Chestnut     Hill     Reservoir,     tempera- 
ture of,  58 

Chlamydomonadina,  237 

Chlamydomonas,  237 

Chlorine,  effect  of,  on  the  growth  of 
microscopic  organisms,  92 

Chlorophyceae,  204 
— ,  seasonal  distribution  of,  104 

Choano-flagellata,  238 

Chroococcaceae,  196 

Chroococcus,  196 

Chydorus,  259 

Chrysomonadina,  235 

Ciliata,  240 

Circulation  periods  in  lakes,  68 

Cladocera,  260 

Cladophora,  217 

Cladothrix,  193 

Classification  of  diatoms,  183 

-  of  lakes  according  to  tempera- 
ture, 64-69 

of    Massachusetts    Ponds    and 

Reservoirs       according       to       the 


microscopic       organisms       present,. 
86-87 

Classification  of  microscopic  organ- 
isms, 171 

— ,  of    microscopic    organisms    ac- 
cording to  their  abundance    81 

Classifications  of  microscopic  or- 
ganisms, schedule  of,  33 

Clathrocystis,  197 

Cleaning  glassware,  directions  for, 
274 

Clean  watersheds,  definition  of,  134 

Closterium,  213 

Cocconeis,  187 

Cocconema,  185 

Cocconideae,  187 

Codonella,  243 

Coelastrum,  209 

Ccelomonadina,  234 

Ccelomonas,  234 

Coelosphaerium,  198 

Cold  Spring  Brook,  color  of,  72 

Coleps,  245 

Collection  of  samples,  apparatus  for, 
269 

Color  of  water,  69-73 
— ,    effect    on   the    growth   of   mi- 
croscopic organisms,  92 

Color  readings,  table  for  transform- 
ing, 274 

Color  standards,  70 

Colpidium,  246 

Coluridae,  254 

Colurus,  255 

Compressibility  of  water,  51 

Concentrating  attachment  to  filter- 
funnels,  Sedgwick -Rafter  Method, 
19-20 

Concentration  of  organisms  by  the 
Sedgwick -Rafter  Method,  18 

Conductivity,  thermal,  of  water,  52 

Conferva,  217 

Confervaceae,  217 

Confervoideae,  217 

Conjugate,  212 


INDEX. 


317 


Connecticut    St.    Bd.    of   Health,    ex- 
amination of  water-supplies,  2 

Conochilus,  251 

Copepoda,  257 

Copper,  use  as  an  algicide,  157 

Corethra,  267 

Coscinodisceae,  191 

Cosmarium,  213 

Counting  -  cell,      Sedgwick  -  Rafter 
Method,  21 

Counting,  methods  of,   by  Sedgwick- 
Rafter  Method,  30 

Crenothrix,  193 

,     growth    in    distribution-pipes, 

165 
— ,    growth    of,    in    ground -waters, 

43>  J5i 
Cristatella,  263 

— ,  odor  caused  by,  123 
Crustacea,  256 

— ,  seasonal  distribution  of,  108 
Cryptomonas,  237 
Crypto-Raphidieae,  190 
Crystal  Lake,  temperature  of,  62 
Cucumber  taste,  123 
Cyanophycese,  195 

— ,  seasonal  distribution  of,  105 
Cyclops,  258 
Cyclotella,  191 
Cylindrospermum,  200 
Cymbella,  184 
Cymbelleae,  184 
Cypris,  260 
Cystiphorae,  196 
Cystoflagellata,  239 

Daphnia,  260 
Decantation  error,  28 
Decapoda,  256 
Decomposition,  odors  of,  120 

—  of  organisms,  131 
Deep  ponds,  organisms  in,  90 
Degree  of  concentration,  24 
Density  of  water,  52 
Desmidieae,  212 


Desmidium,  215 
Diaptomus,  258 
Diathermancy  of  water,  53 
Diatoma,  189 
Diatomaceae,  173 

— ,  cell  of,  173 

— ,  cell -contents,  177 

— ,  classification  of,  183 

— ,  external  secretions,  178 

— ,  growth  of,  at  different   depths, 

102 

— ,  markings,  176 

— ,  movement,  179 

— ,  multiplication  of,  180 

— ,  reproduction  of,  182 

— ,  seasonal  distribution  of,  99 

— ,  shape  and  size,  175 

— ,  structure  of  valve,  177 

— ,  succession  of,  100 
Dictyosphaerium,  207 
Difflugia,  230 
Diglena,  254 
Dimorphococcus,  207 
Dinobryon,  237 
Dino-flagellata,  238 
Disc,    use    of,    for    comparing    the 

turbidities  of  water,  79 
Disintegration,  errors  of,  27 
Dissolved   oxygen    in    Lake    Cochitu- 

ate,  141 
Distribution -pipes,       diminution       of 

microscopic  organisms  in,  161,  164 

— ,    growths   of  organisms   in,    164 
Docidium,  213 

Dolley,    Dr.    C.    S.,    method   of   con- 
centrating microscopic  organisms,  7 
Draparnaldia,  218 

Enchelys,  245 

Encyonema,  185 

Endoparasites     of     man     found     in 

water,  n 

Entomostraca,  256 
Enumeration    of    organisms    by    the 

Sedgwick-Rafter  Method,  23 


INDEX. 


Epistylis,  242 

Epithemia,  187 

Errors       in       the       Sedgwick -Rafter 

Method,  25 
Euastrum,  214 
Eudorina,  211 
Euglena,  234 
Euglenina,  234 
Euglenoidea,  233 
Euglypha,  230 
Eunotia,  187 
Euplotes,  241 

Facultative  limnetic  organisms,  109 
Filter      used      in      -Sedgwick-Rafter 

Method,  15 
Filters,  house,  154 
Filtered  water,  49 
Filter-basins,       (infiltration      basins,) 

growth  of  organisms  in,  45 
Filter-beds,  growth  of  organisms  on, 

150 

Filter-galleries,      (infiltration      galler- 
ies,) growth  of  organisms  in,  45 

Filtration,  154-157 

Fishy  odors,  128-130 

Flagellata,  232 

Flosculariadae,  251 

Floscularia,  251 

Forbes,  F.  F.,  method  of  microscop- 
ical examination,  3 

Forel,    Dr.   F.  A.,    studies   of    Lake 
Geneva,  6 

Fragilaria,  189 

Fredericella,  262 

— ,    growth    of,    in   water-pipes   of 
Boston,  167 

Fungi,  221 
— ,    seasonal    distribution    of,    101 

Funnel  errors,  25 

Oammarus  pulex,  256 
Genevan     Commission,     experiments 
on     the     transparency     of    water, 

77 


Geographical    distribution    of    micro- 
scopic organisms,  81 

Glenodinium,  239 

Gloeocapsa,  197 

Glceocystis,  206 

Gloeothece,  198 

Gomphonema,  186 

Gomphonemeae,  186 

Gonium,  211 

Gonyostomum,  234 

Gordius,  267 

Grassy  odors,  128-130 

Ground-water,  character  of,  42 
— ,  organisms  in,  43,  44,  45 

,  storage  of,  148 

Gymnodinium,  239 

Halteria,  241 

Hardness,    effect    of,    on    the    growth 
of  microscopic  organisms,  95 

Hassall's     method     of    microscopical 
examination,  i 

Hazen,  Allen,    method   of   comparing 
turbidities  of  water,  72 

Heliotropism  of  diatoms,  103 

Heliozoa,  231 

Hensen's    method    of    collecting   mi- 
croscopic organisms,  5 

Heteromonadina,  233 

Heterophrys,  231 

Heterotricha,  242 

Himantidium,  188 

Hippuris,  268 

Holotricha,  244 

Horizontal     distribution     of      micro- 
scopic organisms,  no 

Hyalotheca,  215 

Hydatina,  254 

Hydatinadae,  253 

Hydra,  267 

Hydrodictyon,  208 
— ,  odor  caused  by,  123 

Hypotricha,  240 

Illoricata,  252 


INDEX. 


319 


Individual  Counting  System,  30,  31 
Infusoria,  240 

International  Limnological  Commis- 
sion, 6 

Isomastigoda,  235 
Isopoda,  256 

Jackson,  D.  D.,  attachment  to  filter- 
funnels,  Sedgwick-Rafter  Method, 

J9 

• ,  isolation  of  oil  of  Anabaena,  128 

,  analysis  of  gases  of  decom- 
position of  Anabaena,  131 

Kean,  A.  L.,  method  of  microscop- 
ical examination,  4 

Lake     Cochituate,     temperature     of, 

57-64 

Lake  Winnepesaukee,  temperature 
of,  62 

Lakes,  classification  of,  64 

Lemna,  268 

Leptomitus,  224 

Leptothrix,  192 

Light,  effect  of  light  on  the  growth 
of  diatoms,  101 

,  transmission  of,  by  water,  69 

Limnetic  organisms,  109 

Limnological  Commission  of  Swit- 
zerland, 6 

Limnology,  definition  of,  51 

Littoral  organisms,  105 

Lobosa,  229 

Loricata,  254 

Lyngbya,  201 

Lynn  water-supply,  growth  of 
Raphidomonas,  48 

Lynn  Water  Works  Laboratory,  2 

Macdonald,    J.    D.,    method    of    mi- 
croscopical examination,  i 
Macrobiotus,  267 
Malacostraca,  256 


Mallomonas,  237 

— ,  peculiar  case  of  vertical  distri- 
bution, 114 

Massachusetts  ponds  and  reser- 
voirs, microscopic  organisms  in, 
86 

Massachusetts  State  Board  of  Health, 
examination  of  water-supplies,  2 

Mastigophora,  231 

Mastigocerca,  254 

Melicertadae,  251 

Melosira,  190 

,  odor  caused  by,  123 

Melosireae,  190 

Meridion,  189 

,  odor  caused  by,  122  i 

Merismopedia,  198 

Meyenia,  266 

Micrasterias,  214 

Microcodon,  252 

Microcodidae,  252 

Microcoleus,  202 

Microns,      table      for     transforming, 

273 

Microscopical  examination  of  water,  8 

,  as  indicating  sewage  contam- 
ination, 10 

,  as  explaining  the  chemical 

analysis,  12 

,  as  explaining  the  cause  of  tur- 
bidity and  odor  of  water,  13 

,  as  a  method  of  studying  the 

food  of  fishes,  13 

Microscopical  examinations,  number 
made  in  New  England  and  New 
York,  3 

Micrometer  used  in  Sedgwick-Rafter 
Method,  22 

Micro-organisms,  effect  of,  dpon 
health,  132 

,  use  of  the  term,  9 

,  relative  number  at  various 

depths,  115-116 

Microscope,  outfit  necessary  for  water 
analysis,  22 


320 


INDEX. 


Microcystis,  197 

Monadina,  233 

Monas,  233 

Mt.  Prospect  Laboratory,  2 

Mucor,  223 

Myriophyllum,  267 

Nais,  267 

Nassula,  245 

Natural  odors  of  organisms,  121 

Navicula,  185 

Naviculeae,  185 

Nauplius,  258 

Nematogenae,  198 

Nephrocytium,  207 

Nitella,  219 

Nitrogen,  effect  of,  on  the  growth  of 

microscopic  organisms,  95 
Nitzschia,  190 
Nostcc,  199 
Nostocaceae,  199 
Noteus,  255 
Notholca,  255 
Notommatadae,  254 

Ocular  micrometer  used  in  Sedgwick- 
Rafter  Method,  23 

Odor-producing  substances  in  mi- 
croscopic organisms,  127 

Odors  caused  by  littoral  organisms, 
123 

caused  by  microscopic  organ- 
isms, 120 

caused  by  organic  matter,  118 

caused  by  the  coloring  matter  of 

water,  119 

,  chemical,  131 

,  classification  of  odors  due  to 

organisms,  129 

in  water-supplies,  117,  132 

,  methods  of  observing,  119 

,  natural,  of  organisms,  121 

of  growth,  121 

• of  decomposition,  120 

of  disintegration,  121 


Odors,  terms  describing    their  inten- 
sities, 119 

CEdogoniaceae,  218 

Oil  of  Anabaena,  128 
—  of  Uroglena,  128 
— ,  the  cause  of  odors  in  organisms, 
126 

Oils,    dilution    at    which    their    odor 
ceases  to  be  recognized,  127 

Ophiocytium,  208 

Organic  matter,  removal  from  reser- 
voir sites,  144 

Oscillaria,  177,  201 

Oscillarieae,  201 

Ostracoda,  260 

Oxygen,  dissolved  in  water,  137 

Palmella,  206 

Palmellaceae,  206 

Paludicella,  263 

— ,  growth  of,  in  Brooklyn  water- 
pipes,  263 

Pandorina,  211 

Paramaecium,  244 

Parker,  G.  H.,  method  of  microscop- 
ical examination,  3 

Peck,  Prof.  James  I.,  studies  of  fish- 
food,  7,  13 

Pectinatella,  263 
— ,  odor  caused  by,  123 

Pediastrum,  209 

Pelagic  organisms,  109 

Penicillium,  222 

Penium,  213 

Peridinium,  239 

Peritricha,  241 

Phacus,  235 

Phaeophyceae,  204 

Philodinadae,  252 

Phycochromophyceae,  195 

Phycocyanine,  195 

Phy corny cetes,  223 

Phyllopoda,  259 

Physical  examination  of  water,  8 

properties  of  water,  51 


INDEX. 


321 


Phytoglcea,  29 

Phytozoa,  226 

Pinnularia,  186 

Pipe-moss,  166 

— ,  effect  of,  on  capacity  of  water- 
pipes,  1 68 

Plankton,  definition  of,  5 

Plankton  Net  Method,  34 

Plankton  pump,  7,  38 

Plankton  studies  in  America,  6 

Planktonokrit,  7,  38 

Pleuronema,  246 

Pleurosigma,  186 

Ploima,  252 

Plon  Biological  Laboratory,  6 

Plumatella,  262 

Polyarthra,  253 

Polyedrium,  208 

Polyzoa,  261 

Ponds,  growth  of  organisms  in,  136 

Potamogeton,  268 

Precision  of  the  Sedgwick-Rafter 
Method,  28 

Protococcaceae,  207 

Protococcoideae,  206 

Protococcus,  208 

Protozoa,  225 
— ,  seasonal  distribution  of,  106 

Protozoan  cell,  226 

Pseudo-raphidieae,  187 

Rafter,  Geo.  W.,  improvements  in 
the  method  of  microscopical  ex- 
amination, 4 

Rain-water,  organisms  in,  41 

Raphidieae,  184 

Raphidium,  207 

Raphidomonas,  234 

in  the  Lynn  water-supply,  48 

Rattulidae,  254 

Reproduction  of  diatoms,  182 

Reticularia,  230 

Rhizopoda,  229 

Rhizota,  251 

Rivularia,  203 


Rivularieae,  202 
River-water,  organisms  in,  45 
Rodophyceae,  204 
Rotifer,  252 

Rotifera  ( Rotate ria),  248 
— ,  seasonal  distribution  of,  108 

Saccharomyces,  222 

Sampling,  errors  of,  25 

Sand  error,  26 

Sand  used  in  Sedgwick-Rafter 
Method,  1 6 

Sanitary  water-examination,  data  ob- 
tained by,  8 

Saprolegnia,  223 

Sarcoda,  228 

Scenedesmus,  208 

Schedules  of  classification  of  micro- 
scopic organisms,  33 

Schizonema,  186 

Schizomycetes,  192 
— ,  seasonal  distribution  of,  106 

Schizophyceae,  192 

Scirtopoda,  255 

Scytonema,  202 

Scytonemeae,  202 

Seasonal  distribution  of  Chlorophy- 
ceae,  104 

—  of  Cyanophyceae,  105 

—  of  microscopic  organisms,  98 
Secchi,     experiments    on     the    trans- 
parency of  water,  75 

Sedgwick,  Wm.  T.,  improvements  in 
the  method  of  microscopical  ex- 
amination, 4 

Sedgwick-Rafter  method  of  micro- 
scopical examination ;  4,  15 

Seeding  of  reservoirs  by  organisms 
from  swamps,  136 

Sewage,  microscopical  examination  of, 
ii 

Shallow  ponds,  organisms  in,  86,  90 

Sida,  259 

Siphoneae,  216 

Sirosiphon,  202 


322 


INDEX. 


Sirosiphoneae,  202 

Smith,    H.    L.,    classification    of    di- 
atoms, 184 

Soil  removal,  146 

Sorastrum,  209 

Sorby,  H.  C.,  method  of  microscop- 
ical examination,  2 

Sphagnum,  251,  267 

Sphaerozosma,  215 

Sphaerozyga,  199 

Spirogyra,  216 

Sponge,    growth    of,    in    water-pipes, 
165-166 

Spongidae,  264 

Spongilla,  265 

- — ,  odor  caused  by,  123 

Spring    overturning    (spring    circula- 
tion), 60 

Stagnant    pools,    growths    of    organ- 
isms in,  137 

Stagnation,  59-61 

,  effects  of,  103,  138 

Statoblasts,  262 

Standard  Unit,  29,  31 

Staurastrum,  214 

Staurogenia,  209 

Stauroneis,  186 

Stentor,  243 

Stephanodiscus,  191 

Stigeoclonium,  218 

Storage  of  ground-water,  148 

Storage  reservoirs,  low-level  gate,  147 

,  soil  to  be  removed  from  site  of, 

146,  147 

Storage  of  surface-water,  134 

Stratification  of  water,  52 

Suctoria,  246 

Surface-water,  organisms  in,  45 
— ,  storage  of,  134 

Surirella,  190 

Surirelleae,  190 

Swamps,  effect  of,  on  water,  135 
— ,  growth  of  organisms  in,  135 

Synchaeta,  253 

Synchaetadae,  253 


Syncrypta,  236 
Synedra,  188 
Synura,  235 
— ,  odor  caused  by,  124 

Tabellaria,  189 

Tabellarieae,  189 

Taste,  its  relation  to  odor,  117 

Temperature  of  lakes  and  ponds,  53 

-  of   water   in    distribution-pipes, 
160 

-  of  water,   methods  of  observa- 
tion, 53 

Tentaculifera,  246 

Tetmemorus,  214 

Tetrapedia,  198 

Tetraspora,  206 

Thermocline,  63 

— ,  its  relation  to  the  vertical  dis- 
tribution of  microscopic  organisms, 
114 

Thermophone,  54-57 

Tintinnidium,  242 

Tintinnus,  242 

Trachelocerca,  246 

Trachelomonas,  235 

Transparency  of  water,  77 

Triarthra,  253 

Triarthradse,  253 

Trinema,  230 

Tubifex,  267 

Turbidity  of  water,  74-76 

Ulothricheae,  218 
Ulothrix,  218 
Unit,  Standard,  29,  31 
Uroglena,  236 

—  oil  isolated,  128 
Utricularia,  268 
Uvella,  236 

Vaucheria,  217 
Vaucheriaceae,  216 

Vertical    distribution    of    microscopic 
organisms,  in 


INDEX. 


323 


Volvocina,  238 
Volvocineae,  210 
Volvox,  210 
Vorticella,  241 

Water  analysis,  value  of,  9 

Water-pipes,  growth  of  organisms  in, 
160 

Weights  and  measures,  conversion 
tables,  272 

Wind,  effect  of,  on  horizontal  dis- 
tribution of  microscopic  organ- 
isms, no 


Wind,  effect  of,  on  vertical  distri- 
bution of  microscopic  organisms, 
"3 


Xanthidium,  214 


Zoogloea,  29 
Zoothamnium,  242 
Zygnema,  216 
Zygnemaceae,  215 
Zygogonium,  216 


PLATE  I. 

DIATOMACE&. 


PLATE  I. 
DIATOMACEJE. 

Magnification  500  diameters. 

Fig.  A.  Navicula  viridis,  valve  view. 
B.  Navicula  viridis,  girdle  view. 
;     C.  Navicula  viridis,  transverse  section. 

a,  Outer,  or  older  valve,    b,  Inner,  or  younger  valve,     c,  c',  Con- 
nective bands,  or  girdles,     d,  Central  nodule-     ce,  Terminal 
nodules,     f,  Raphe.     g,  Furrows,     in,  Chromatophore  plates. 
n,  Nucleus,    o,  Oil  globules.    />,  Cavities.    «,  Protoplasm. 
Figs.  D,  E,  F.  Navicula  viridis,  sectional  views  showing  multiplication  by 

division.    After  Deby. 

a,  Valve,  b,  Girdle,  c,  Protoplasm,  d,  Chromatophore 
plates,  e,  Central  cavities,  f,  Nucleus  and  nucleolus. 
g,  Oil  globules. 


.  i.  Amphora,  valve  view. 
2-  Amphora,  girdle  view. 

3.  Cymbella,  valve  view. 

4.  Cymbella,  valve  view. 

5.  Encyonema.    A,  valve  view.    B,  girdle  view. 

6.  Cocconema.    A,  valve  view.    B,  girdle  view. 

7.  Navicula  gracilis,  valve  view. 

8.  Navicula  Rhyncocephara,  valve  view. 

9.  Stauroneis,  valv^e  view. 

10.  Stauroneis,  girdle  view. 

11.  Pleurosigma,  valve  view. 

12.  Gomphonema.     A,  valve  view.    B,  girdle  view. 

13.  Cocconeis,  valve  view. 

14.  Cocconeis,  girdle  view. 

15.  Epithemia,  valve  view. 

16.  Epithemia,  girdle  view. 

17.  Eunotia,  valve  view. 


PLATE  I 


PLATE   I!. 

DIATOMACEJE. 


PLATE  II. 
DIATOMACEJE. 

Magnification  500  diameters. 

Fig.  i.  Himantidium,  valve  view. 
"     2.  Himantidium,  girdle  view. 
"  w'3.  Asterionella,  valve  view. 
"     4.  Asterionella,  girdle  view  (typical  form). 
"     5.  Asterionella,  girdle  view,  showing  division  of  the  cells. 
'    6.  Asterionella,  girdle  view,  showing  rapid  multiplication. 
"    7.  Asterionella.    A,  valve  view.    B,  girdle  view. 
"  ^8.  Synedra  pulchella,  valve  view. 
;     9.  Synedra  pulchella,  girdle  view. 
"  10.  Synedra  ulna,  valve  view. 
"'  ii.  Synedra  ulna,  girdle  view. 
"n.2..  Fragilaria,  girdle  view. 
"  13.  Fragilaria,  valve  view. 


PLATE  II 


G.C.W.oW. 


PLATE  III. 

DIATOMACE^E. 


PLATE  III. 
DIATOMACE;E. 

Magnification  500  diameters. 


Fig.  i.  Diatoma  vulgare,  valve  view. 
"     2.  Diatoma  vulgare,  girdle  view. 
"     3.  Diatoma  tenue,  girdle  view. 
"     4.  Meridion  circulare,  valve  view. 
:     5.  Meridion  circulare,  girdle  view. 
"    6>  Tabellaria  fenestrata,  valve  view. 
*'     7.  Tabellaria  fenestrata,  girdle  view. 
"    8.  Tabellaria  flocculosa,  valve  view. 
"    9.  Tabellaria  flocculosa,  girdle  view. 
e<  10.  Nitzschia  sigmoida,  valve  view. 
"  ii.  Nitzschia  sigmoida,  girdle  view. 
"  12.  Nitzschia  longissima,  girdle  viev/. 
"'  13.  Surirella,  valve  view. 
"  14.  Surirella,  girdle  view. 
"  15.  i^vlelosira,  valve  view. 
"  16.  Melosira,  girdle  view. 
"  17.  Melosira  auxospore. 
"  i8.v  Cyclotella,  valve  view. 
"  19-  Cyclotella,  girdle  view. 
"  20.  Stephanodiscus,  valve  view. 
"  21.  Stephanodiscus,  girdle  view. 


PLATE 


G.C.W.<W  • 


PLATE   IV. 

SCHIZOMYCETES.     CYANOPHYCE^E. 


PLATE  IV. 

SCHIZOMYCETES. 
Magnification  500  diameters. 

Fig.  i.  Leptothrix. 

"     2.  Cladothrix,  showing  false  branching. 
"     3.  Breggiatoa. 

"     4.  K^renothrix.     A,   filament    enclosed   in    sheath.     B,   filament   with 
sheath  removed,  showing  liberation  of  spores. 


CYANOPHYCEyE. 
Magnification  500  diameters. 

Fig.  5.  Chroococcus.  Fig.iovCcelosphjcrmm. 

,6.  Gloeocapsa.  "  n.  Merismopedia. 

7.  Aphanocapsa.  i^  12.  Nostoc. 

8>^vTicrocystis.  "^3-  Anabaena  flos-aqn<T. 

9.  Clathrocystis.  "  14.  Anabsena  circinalis. 


PLATE  IV, 


•  9 
0« 


G.C.W.oW 


PLATE  V. 

CYANOPHYCE&.     CHLOROPHYCE^E. 


PLATE  V. 
CYANOPHYCEjE, 

Magnification  500  diameters. 

Fig.  i.  Sphserozyga.  Fig.  6.  Microcoleus. 

:     2.  Cylindrospermum.  "     7,  Scytonema. 

3.  Aphanizomenon.  "     8.  Sirosiphon. 

4.  Oscillaria.  L  "    9.  PJvularia,  a  single  filament. 
;    5.  Lyngbya. 

CHLOROPHYCE/E. 

Magnification  500  diameters. 

"  10.  Gloeocystis.  "  Fig.  12.  Tetraspora. 

"  ii.  Palmella. 


PLATE  V 


PLATE  VI. 
CHLOROPHYCE^E, 


PLATE  VI. 
GHLOROPHYCEJE. 

Magnification  500  diameters  (except  Fig.  9). 

Fig.  i.  Botryococcus.  Fig-  7.  Polyedrium. 

"    2.  Raphidium.  *L>*^v8.  Scenedesmus. 

*'     3.  Dictyosphjerium.  L^'    9.  Hydrodictyon.     x  250. 

"    4.  Nephrocytium.  "  10.  Ophiocytium. 

"     5    Dimorphococcus.  I?  n.  Pediastrum. 

I  "    6.  Protococcus.  "  12.  Sorastrum. 


PLATE   VI 


12 


,3 


8 


10 


II 


. 


G.CW.tfe/ 


PLATE  VII. 

CHLOROPHYCE&. 


PLATE  VII. 


Fig.  i.  Ccelastrum.     x  500.  ^Fig.  8.  Closterium  Dian?e.     x  250. 

;     2.  Staurogenia.     x  500.  "     9.  Closterium      Ehrenbergii. 

"    3-wv/'olvox.    x  100.  x  250. 

'    4.  Eudorina.     x  250.  "  10.  Closterium  subtile,     x  250. 

"     5.  Pandorina.     x  250.  "  n.  Docidium.    x  250- 

*'    6.  Gonium.      a,    top    view.  \S*^I2.  Cosmarium.     x  250. 

&,  side  view,  x  500.        "  13.  Tetmemorus.    x  250. 
"     7.  Penium.     x  250. 


PLATE    VII 


8 


12 


13 


K 


> 


-C.yv.de/. 


PLATE  VIII. 
CHLOROPHYCE^E. 


PLATE  VIII. 

CHLOROPHYCE7E. 

Magnification  250  diameters. 

LFig.  A.  Cosmarium,  showing  division. 

Figs.  B,  C,  D,  E,  and  F.  Cosmarium,   showing  conjugation,   formation   of 
zygospore  and  germination  of  the  spore. 


Fig.  i.  Xanthidium  armatum. 
"     2.  Xanthidium  antilopaeum.     a,  front  view,     b,  lateral  view,     c,  end 

view. 

:     3.  Arthrodesmus.    a,  front  view-    b,  end  view. 
"     4.  Euastrum.    a,  front  view,    b,  lateral  view. 

5.  Micrasterias. 

L,  "     6.  Staurastrum  magnum,    a,  front  view-    b,  end  view. 
"    7-  Staurastrum  macrocerum.    a,  front  view,    b,  end  view. 


PLATE  Vlll 


5 


G.C.W.oW. 


PLATE   !X. 
CHLOROPHYCE^E. 


PLATE  IX. 
CHLOROPHYCE/E. 

Fig.  i.  Hyalotheca.    a,  filament,     b,  end  vi.w.     x  500. 
"    2.  Desmidium.    a,  filament,     b,  end  view,     x  500. 
:     3.  Sphserozosma.     a,  filament,    b,  end  view,     x  500. 
:    4.  Spirogyra.     x  125. 

:    5.  Spirogyra,  conjugated  form,  showing  spores.    xi2,5° 
L>*    6.  Zygnema.    x  125. 
7.  Vaucheria.    x  100. 
:    8.  Conferva,    x  125- 
r    9.  Cladophora.    x  75- 
"  10.  Ulothrix.    x  125. 


PLATE  IX 


2  I 


'    .« 
- 


a 

A 


*•     -^ 


, 

>  m 


10  / 

^MH 


• 


G.C.W.rfn! 


PLATE  X. 

CHLOROPHYCE^E.    FUNGI. 


PLATE  X. 
CHLOROPHYCEJE. 


Fig.  i.  Draparnaldia.      x  125. 
"     2.  Stigeoclonium.  x  125. 


Fig.  4.  Saccharomyces.    x  500. 
:    5.  Mold  hyphae.    x  250. 
1    6.  Penicillium.    x  250. 


Fig.  3.  Chsetophora.     x  125. 


FUNGI. 


Fig.  7.  Aspergillns.    x  250. 
"    8.  Mucor.     x250. 


PLATE  X 


6 


G.C.W.A/ 


PLATE  XI. 

FUNGI.    PROTOZOA. 


PLATE  XI. 
FUNGI. 

Fig.  i.  Saprolegnia.     x  250.  Fig.  3.  Leptomitus.    x  500. 

"    2.  Achlya.    X250. 


PROTOZOA. 

ig.  4.  Amoeba,    x  250.  Fig.  8.  Euglypha.     x  250. 

5.  Arcella,  lateral  view,    x  250        "     9.  Trinema.     x  250. 
(    6.  Arcella,  inferior    view.  x25o      "  10.  Actinophrys.     x  250. 
"    7.  Difflugia.    X250. 


PLATE  XI 


G.C.W.oW. 


PLATE  XII. 

PROTOZOA. 


PLATE  XII. 
PROTOZOA. 

Fig.  i.  Cercomonas.     x  500.  Fig.  8.  Bftacus.     x  500. 

2.  Monas-    x  500.  "  9.  ifeyntira.     x  500. 

:    3.  Anthophysa.    x  500.  "  10.  Uvella.     x  500. 

;     4.  Coelomonas.    x  500.  "  11.  Syncrypta.     x  500. 

;     5.  Raphidomonas.     x  500.  "  I2i/fjroglena.     x  250. 

6.  Euglena.     x  500.  "  13.  Uroglena;  showing  division 

"    7-  Trachelomonas.     x  500.  of  the  monads,     x  1000. 


PLATE  XII 


0 


13 


5 


.  «  • 


8 


**lil 

•  :  W?*\\ 

ikWittfr, 


G  .C.W.  del. 


PLATE  XIII. 

PROTOZOA. 


PLATE  XIII. 
PROTOZOA. 


Fig.  i/Dinobryon.    x  500.  Fig.  7.  Glenodinium.    x  500. 

"    2>Cryptomonas.    x  500.  "    8.  Euplotes.     x  250. 

"    3.  Mallomonas.     x  500.  "    9.  Halteria.    x  500. 

"    4.  Chlamydomonas.     xiooo.          "  10-  Vorticella.    X25O. 

"    5>  Peridinium.    x  500.  "  n.  Epistylis.    x  250. 

*"**    6.  Ceratium-    X250.  "  12.  Tintinnus.    X250. 


PLATE  XIII. 


G.C.W.oW. 


PLATE  XIV. 

PROTOZOA. 


PLATE  XIV. 

PROTOZOA. 


Fig.  i.  Codonella.     x  500.  Fig.  6.  Coleps.     x  500. 

"    2.  Stentor.     x  50.  "     7.  Enchelys.     x  500. 

"    3.  Bursaria.    x  100.  "    8.  Trachelocerca.    x  500. 

s^    4-  Paramsccium.     X250.  "    9.  Pleuronema.    x  500. 

"    5.  Nassula. 


PLATE  XIV. 


" 


G  .C.W.  del 


PLATE  XV. 

PRO  TOZOA .    RO  TIFERA. 


PLATE  XV. 

PROTOZOA. 
Fig.  i.  Colpidium.    x  500.  Fig.  2.  Acineta.     x  500. 


ROTIFERA. 

Fig.  3.  Floscularia.     x  25.  Fig.  6.  Rotifer,     x  100. 

:    4.  Melicerta.     x25-  "    7.  Microcodon.     x  150. 

"    5.  Conochilus.     x  100.  "    8.  Asplanchna.    x  150. 


PLATE  XV 


8 


-.7 


G.C.W.oW' 


PLATE  XVI. 

ROTIFERA. 


PLATE  XVI. 


Figs.  A  to  E.  Diagrams  of  Trochal  Disc.     (After  Bourne.) 

A,  Microcodon.     B,  Stephanoceros.     G,  Hypothetical  form 
intermediate  between  Microcodon  and  Philodina.     D, 
Philodina.     E,  Brachionus. 
Figs.  F  to  I.     Diagrams  showing  Structure  of  the  Foot.     (After  Hudsor 

and    Gosse.) 

F, Rhizotic  foot  (Floscularia).    G, Rhizotic  foot  (Melicerta) 
H,     Bdelloidic    foot     (Rotifer).       I,     Scirtopodic    foot 
(Pedalion). 
Figs.  J  to  P.     Diagrams  showing  Forms  of  Trophi.     (After  Hudson  and 

Gosse.) 

J,  Malleate.  K,  Sub-malleate.  L,  Forcipitate.  M,  In- 
cudate.  N,  Uncinate.  O,  Ramate.  P,  Malleo- 
ramate. 


Fig.  i.  Synchseta.    x  100. 
"    2.  Polyarthra.     x  200. 
"    3-  Triarthra.    x  150. 


ROTIFERA. 


Fig.  4.  Diglena.     x  15°- 
"    5.  Mastigocerca.    x  150. 


PLATE  XVI 


H 


K 


'>      1 


M 


N 


7( 


I 


. 


A 


G. CW.de/. 


PLATE  XVII. 

ROTJFERA.     CRUSTACEA. 


PLATE  XVIT. 
ROTIFERA. 

Fig.  i.  Brachionus.     x  200.  VXFig.  3.  Anuraea  aculeata.     x  ISO. 

"    2.  Anuraea  cochlearis.    A,  dor-      "    4.  Notholca.     x  200. 
sal  view.  B,  side  view. 


CRUSTACEA. 

"  Fig.  5.  Cyclops,    x  25.  Fig.  8.  Cypris.    x  25. 

^"    6.  Diaptomus.     x  25.  "    9.  Daphnia-    x  25. 

"    7.  Canthocamptus.    x  25.  "  !'«">•  Bosmina.    x2$. 


PLATE  XVII. 


G.C.W.rfrf 


PLATE  XVIII. 

CRUSTACEA.    BRYOZOA.     SPONGID^E. 


PLATE  XVIII. 
CRUSTACEA. 

Fig.  i.  Sida.    x^S.  Fig.  3.  Branchipus.     x2. 

"    2.  Chydorus.    X25. 

BRYOZOA. 

Fig.  4.  Fredericella.    x  5-  Fig.  6.  Statoblast  of  Plumatella. 

"    5.  Paludicella.    x5-  "    7-  Statoblastof  Pectinatella. 

SPONGID^:. 

Fig.  8.  Spongilla.    x  i. 
"    9.  Sponge    spicules     (skeleton  spicules).    x  150. 


PLATE    XVIII 


G.C.W.oW. 


PLATE  XIX. 

MISCELLANEOUS. 


PLATE  XIX. 

MISCELLANEOUS. 

Fig.  I.  Anguillula.    x  100.  Fig.  7.  Batrachospermum.     x  100. 
"    2.  Nais.    x  10.  "    8.  Chara.    x  75- 

"    3.  Chastonotus.     X250.  "    9.  Anacharis.     x  i. 

"    4-  Macrobiotus.    x  250.  "  10.  Ceratophyllum.     x  I. 

"    5.  Acarina.     x2S.  "  n.  Potamogeton.    XL 

"    6.  Hydra,     x  25.  "  12.  Lemna.     x  I. 


PLATE  XIX, 


G  .C.W.  M 


GENERAL  LIBRARY 
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MOV      6  1954 


NOV      $  1954 


NOV     8  1954 
OCT  2  5 


NOV      8 


J954 
1954 


OC 


NOV  1  0  1954 
9     1954 

1955 


JUN  1  5  1955 


21-100m-lf'54(1887sl6)478 


NOV    9  1956 


H 


MAR  12  1964 
FED  2  7  1964 


MAR  .17  '964 
MAR  1  8  1964 


APRS    1966 
AP8'66BI 

F      6    1969 
MAR  2  ia 

FEB  -2  1972 

JAN  2  5  1972     2 


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